This is Jay Leno's year. This is Jay Leno's decade. Heck, maybe this is Jay Leno's planet; you never know. Jay Leno is a, if not the, comedian for our time, arguably unarguably the best of the aging young comics, although you might get an argument on that.

You gotta love this guy. You just gotta. You do, don't you?

"I think," says Jay Leno, "it's a genetic fault that makes you want to get up and stand up in front of people. We just happen to live in a time when being funny is an asset. If I was the funniest guy in Attila the Hun's army, I'd be dead now. I would be of absolutely no value to these people at all."

In his big "Dave-Clark-Five-Beatle boots," shaggy jeans and tinselly jackets from the kicky second-hand shops on L.A.'s trendy Melrose Avenue, Jay Leno, 36, is an open if unlikely invitation to a laugh. Once turned down for a TV series on the grounds that he would "frighten children," and rejected at a commercial audition because he didn't look "American" enough, Leno's back-alley black hair and jutting Dudley Do-Right chin might actually be intimidating if not for the friendly-goofy look on his puss.

He's a merry Mack, a japester, a peerless inventive instigator of rollicking guffaws and wacky chuckles. He's not just a comic; he's a stand-up social commentator, a sarcastic reprocessor of American pop culture and, not coincidentally, a roving TV critic as well.

"The most embarrassing show to me every year is the People's Choice Awards," Leno says. "I don't know who these 'people' are, but they should have the freedom of choice taken away from them. There's one joke that I do, it never works, I just like the joke: I say you can see where the education in this country is going from the fact that Robert Blake and Mr. T can beat our Sartre and Descartes for Best Philosophers on the People's Choice Awards.

"And a few people get it, but most people have no idea what I'm talking about."

Born in Boston, and reared there as well, Leno changed careers about 15 years ago from Rolls-Royce and Mercedes-Benz mechanic to comedian. He has comeded up and down the length and breadth of this great land of ours, and now all those years of playing comedy clubs and colleges and, yes, a Washington strip joint have paid off. In addition to a recent sold-out concert at the Warner Theatre here, Leno also played to a packed house at, ooooh, New York's famed Carnegie Hall.

"You know, it's funny, the thing about Carnegie Hall is, people think you have to be chosen," Leno says, smiling. "They think the Carnegie Foundation sits down and men with glasses go, 'Oh, Jay Leno, he's up for approval. Any problems on that?' It's like when I worked for Rolls-Royce, people would say, 'Now, do you have to have any special credentials?' No. All you need is the cash and you can buy one. You can be a pimp."

Ah that Jay Leno. Self-effacing to a fault. "Jay Leno at Carnegie Hall" still sounds impressive. "Oh yeah, but two nights later I'm at the Mechanics' Hall in Worcester. You know, then you're at Joe Bosco Technical High School Auditorium three nights after that."

But he's all over television as well. His appearances on "Late Night With David Letterman" have been so consistently hilarious that he's now a semiregular, appearing about once a month (next appearance: late May), often brandishing a TV Guide and reporting on the latest TV movie to use the tattered "evil twin" gambit. He hosted "Saturday Night Live" earlier this year. And he's reading sitcom scripts, though he says he has his doubts about finding something suitable.

In May, Showtime, the pay-cable network, will render unto its subscribers "Jay Leno and the American Dream," an inventive special that includes some of Leno's stand-up material and clever bits taped on location around the Midwest. Last month, Leno popped up four nights one week at the beginning of prime time on NBC, introducing the lineup with his own acerbic glint.

Of a "Riptide" episode dealing with the appearance of a lost Shakespearean play, Leno told viewers, "Well, let's think about it. If a new Shakespeare play did surface, where else would you see it but 'Riptide'?"

However, he does feel a little guilty about venturing into that compromising position known as Prime Time.

"Does it seem like it's selling out?" he wonders worriedly aloud. "You know, the only time you can be a comedian on TV is after 11:30 at night. That's it. I mean, you can possibly show up as the boyfriend on a sitcom or something, but if you're a comedian, the only place you can be seen as a comedian is late at night. And I find people either know who I am or have NO IDEA."

What Leno does is not so much joke comedy, but attitude comedy. He stands back and takes a look and makes fun. He reads a news item and plays it back with its absurdity enhanced. Like when he read that Charles Manson was going before the parole board again. He speculated on what Manson would have said to his cell mate just before the appearance: "Gee, what do you think, Bob -- the blue tie? Too busy?"

He sees ads on television for what he calls the "Time-Life Atrocity Series," books that glorify killers and bandidos of yesteryear, and wonders what will be peddled to eager readers 100 years from now: "Read about John Hinckley Jr., an hombre so ornery, he once shot a president -- just so he could meet a pretty gal!"

Television, inevitably, is a rich source for Leno. But comedians, even comedians of High Moral Principle, are like salesmen; they are desperate to be liked by one and all. So Leno doesn't deride television. He just rides it.

"I always contend you can make fun of TV and think it's stupid and still watch it," he says. "I always get annoyed at the type of performers who make fun of things from above. You can make fun of it from within. Just because I go to a fast-food restaurant doesn't mean I can't make fun of it. And it's the same with television. You can watch it and still think it's stupid and tear it apart.

"I don't really attack television. I think I just poke fun at how stupid 'they' think 'we' are. Television is a great source only because it's what everybody knows. In the old days, when a comic would travel around, once he left New York and went into, quote, the sticks, he would do, 'Here's the drunk at the ballpark on New Year's Eve ladies and gentlemen,' you know, or some generic piece of humor. So in place of that now you do television, because everybody, everybody, knows 'The A-Team.' Political humor is almost impossible to do."

Leno turned down an invitation to be part of the recent "Comic Relief" benefit in part because it conflicted with his Carnegie Hall concert, in part because he sensed an anti-Reagan political cast to it. "I'm not a Reagan fan, but if I want to make fun of the president, I will do it my way," he says. "I don't like to be involved in something where other people are speaking for me, going 'Reagan, what an (bleep), that (bleep), what a (bleep), here's Jay Leno.' " Here's Jay's Roots

Jay Leno has been the opening act for singers as disparate as Perry Como and James Brown. He opened in Las Vegas once, completely unbilled, for Tom Jones ("To me, the strangest thing I saw in Vegas was a woman nursing her baby at the slot machines"). As preparation for this career, Leno remembers flushing tennis balls down toilets in high school and getting big laughs, and he remembers all those report cards on which teachers had written, "Jay has the ability but does not apply himself."

Yes, Jay Leno remembers all that. But mostly what he remembers are Jay Leno's Nightmare Gigs. Through them he earned not just his comedy stripes and his comedy wings, but his comedy purple heart.

At Emerson College, in Boston, where he was a student, Leno would emcee amateur talent shows and work in a few shy jokes. "They'd put a candle on a table in the cafeteria and call it the Two-Toke Cafe and I would emcee a lot of these shows. At that time in the early '70s it was 19-year-old kids with guitars: 'My life is over,' you know, and they fall off the stool and it would be my job to come on stage and drag this carcass off and say, 'Okay, here's so-and-so, another guy from Long Island with a guitar.' "

Years passed, and soon Jay was playing colleges as a professional comedian, sort of. He remembers driving eight hours from Boston to a small college in upstate New York and getting paid $25 a day for three days of performances. Little did he know he would suffer the torture of the damned: Jay Leno's Nightmare Gig No. 1!!!

It went something, just a little bit, or actually quite a lot, like thisssss . . .

"So I go up there, and I'm stayin' in a dorm, and they say, 'Okay, you're in Study Hall C at 9.' I go to Study Hall C; there's a thumb tack with an index card: 'Tonight Jay Leno.' Doesn't say what I do. So I walk in at 9, and there's kids studying. Six girls come in and they go, 'Okay, everybody, we have a comedy show here!' 'Hey, shut up, we have a test!' So they bring this little toy mike and this speaker and I have to hold the speaker in my hand and aim it at whoever I was talking to. And I do like 45 minutes with people just going, 'Shut up, shut up!'

"So after the show I say, 'Listen girls, this isn't going to work out.' They say, 'Oh? Well we're going to call your agent and tell him you're uncooperative.' I said okay. I come back the next night. Study Hall C again. It's the same kids! 'We saw him last night. Shut up, you're not funny! Shut up, shut up, why don't you go home?'

"The third day, I'm sitting there in the cafeteria eating and these three girls walk by me and one of them goes, 'There's that jerk that thinks he's a comedian.' 'Which one?' 'That stupid guy over there.' "

But Jay Leno was not daunted. Jay Leno pressed on. And before much longer, Jay Leno was ready for Nightmare Gig No. 2: George Washington University, Washington, D.C. . . .

"Yeah, I opened for Rare Earth. Do you remember Rare Earth? They had this big single, 'Get Ready.' I was 23 years old, I come down, and the audience is all neighborhood kids from the area, mostly teen-agers, mostly boys about 15 years old. So I get here and they're all screamin' and yellin' and the Rare Earth manager says, 'Hey listen, Rare Earth's got a lot of expensive stuff on the stage, you can can't use the stage. You've got to stand on the gym floor.'

"I said okay. So I'm standing on the floor, facing an audience who is also standing; we're standing, facing each other, and I've got the mike in my hand and I'm talking and I see the mike cord going through the crowd. So I'm about two minutes into this thing, 'Thank you very much,' all of a sudden, somebody jerks the cord and the mike goes boom, boom, boom, on the floor and off through the audience.

"Now I'm running through a bunch of kids chasing the microphone and trying to grab it and this guy's going, 'Hey bro, what's happenin'?' And I'm, 'Hey, give me that! Give me that mike!' Never did get the mike back. They docked me $75 out of my pay for it.

"It was so stupid. It was the most horrible job. I mean, it was unbelievable. But -- that's show biz."

Stupid? Horrible? Unbelievable? But that's show biz? Maybe so, but it was nothing compared to Nightmare Gig No. 3: Lenny's on the Turnpike, Boston, Mass., U.S.A. You remember. It all started when the crowd got restless for Buddy Rich, the famous drummer . . .

" . . . and there's a woman on stage singing, and the audience is going, 'Boooo, get off, you're a slut.' So this woman goes 'Arrgghhh' and runs off crying, and the audience goes, 'All right, yeah, get her out of here!' So, the emcee says, 'We've got a bright young comedian.' 'Booooo!!!.' He says my name and this guy stands up and says, 'We hate him!' Now I had never appeared anywhere. I said, 'How can they hate me?'

"So I walk out on stage. 'Thank you very much, great to be here.' 'Boooo, boooo' -- they're screaming and yelling and this kind of Mafia guy in the front goes, 'Hey, get Buddy out here or I'm going to smash your face!' And I said, 'Well, sir,' and he said, 'Get him out here right now or I'm going to smash your face.' So I figured, I'll try to be friends with this guy. And I leaned over and said, 'So, where you from?' And the guy jumps up and, BAM, just decks me. BOOM. And I fall down.

"So I'm lying there, bleeding, and Lenny, the owner, is saying, 'Come on, get up and finish,' and there's a couple sitting ten feet away and they didn't even see it, they didn't even see me knocked down. So I struggle back up again, and now two guys are holding this Mafia guy so he can't hit me again, and I went on and somehow I managed to finish. And I got my $25, and my agent was waiting there to take his $2.50 commission. That was the funniest thing. I had to break a five to give him his commission."

But was Jay discouraged? Was Jay dismayed? Did Jay give up? No! And why? Because: he wanted to go on to make a lot of money. And he did. Jay and Dave

"Jay is nothing if not diplomatic," says David Letterman, godfather of modern American television comedy and big Jay Leno fan.

We thought it would be funny if, unbeknownst to Jay, we tried to lure him into a feud with Dave! Here's how it went . . .

"Now what about Letterman? The guy seems to be going a little over the edge. Have you watched him lately? He runs wild."

"Oh, no. I think David's much more relaxed now than he was at the beginning. Oh sure." (Tee-hee-hee! He's going for it!)

"Did you see him the night he spotted someone he didn't know in the studio and threw the guy bodily out, ran him down the hall, put him on an elevator, and it turns out it was a writer from Sports Illustrated?"

"No, I didn't see that."

"How about the night he was running around with ice, claiming there wasn't enough ice in the green room?"

"No. I only get to see it about twice a week."

"Well, I just told you about two incidents. Doesn't that sound like the ravings of a madman?"

"No, that sounds like -- that sounds like Letterman, actually. That sounds like Letterman."

"Aren't you really just FED UP with him?" (Jay is remaining PERFECTLY CALM through all these questions.)

"No, no, not at all. You know David is an interesting character. I don't know how to describe him."

"You've never been to Dave's house, have you?"

"Yeah, well, once a couple of guys and I went to his place and tore up his front yard with our motorcycles."

"But that was when he was living in California."

"Yeah, yeah. No, I haven't been to Dave's place in Connecticut."

"So he's sort of a reclusive, antisocial guy?"

"No, not really. David and I do not have a lot in common, but I think we have a mutual like for each other's sense of humor. Like David has always made me laugh, even from the first day I saw him audition at the Comedy Store years ago. He had a big red beard; he looked like Dinty Moore. I watched him and he was just about as good on the first day as he is now."

"Oh -- he hasn't improved at all?"

"No, I don't mean it that way." (Oh boy! Is Jay ever starting to squirm! Well, actually, no, he isn't. He isn't squirming at all. After all, this is nothing compared to Lenny's on the Turnpike. But then, that's another thing that makes Jay Leno different from a lot of comedians. On stage he's loud, he's sarcastic, he's crazy, he heckles the hecklers, but he is never mean. He is never cheap. He's taken his licks, he's paid his dues, he's been a poet, a pirate, a pauper, a poet -- oh, we already said poet -- but through it all, he has remained, not just America's favorite young comedian, but a heckuva helluva darn damn decent guy). Jay's Comedy Credo

In his act, Leno gives comedic voice to so many grievances against the system that he is asked if he is sort of an ombudsman as well as a comic. He says one thing he never wants to be is a spokesman.

"I don't think I'm breaking any new ground," he says. "I'm not doing anything different. It's just a matter of how you choose to do it. I would rather make fun of the corporation or whatever it is that dehumanizes people than make fun of the people themselves. Nowadays you make fun of nuclear power, the phone company, giant computers that send people $90,000 phone bills; you laugh at that because here is a chance for the human spirit more or less to triumph over the machine.

"I mean, I'm not some Che Guevara of comedy out there, with, you know, 'Here's the truth.' I'm not Howard Beale. Because pomposity is real easy to get into in comedy. You know, you wait for a comic to come on the Carson show and they sit down and they go, 'You know, Johnny, we were just in Moscow, and the Russian people are just like us, I find them refreshing and likable and -- ' Oh, shut up!

"I pick up a newspaper; it says I'm doing something totally different in comedy. There's nothing really different that hasn't been done before in one style or another. You know, it all comes down to good jokes. It all comes down to whether it's funny or not."