Lazy conventional wisdom has it that "Saturday Night Live's" best times are behind it. Well, whose aren't? To judge by the show's season premiere and its recent triumphant 25th-anniversary special, however, its worst times are way behind it, too.

An upstart that became an institution, "SNL" began its 25th season Saturday with the huge plus of Jerry Seinfeld as guest host. Except for his lavishly produced American Express commercials, Seinfeld had been absent from broadcast TV since the finale of his great sitcom "Seinfeld" in 1998. He received truly tumultuous applause from the studio audience when he came onstage, and emotionless as Seinfeld often seems, the ovation did appear to impress even him.

No new sitcom has come along to replace "Seinfeld" in the hearts and minds of the national audience in the dry interim, and "Seinfeld" reruns in syndication have proved themselves endearing and durable no matter how many re's they're run.

Seinfeld's opening monologue ostensibly briefed viewers on his activities post-"Seinfeld" and ended with the quickly muttered aside "Plus I dated a couple married women," a reference to tabloid headlines.

On "SNL" you must be ready and willing to spoof yourself, and one of the sketches on the premiere had Seinfeld updating his sitcom's finale--the whole cast in jail--by showing him in the prison to which he was sent. It happened to be the prison from "Oz," HBO's grim, gritty and literally penetrating series about convicts and their capers.

This sequence was filmed on the "Oz" set with the cooperation of "Oz" producer Tom Fontana and several members of the show's cast. It was a double parody of both shows, and dead on--a two-headed light saber of satire.

Seinfeld had other high points, including an appearance with regular cast member Ana Gasteyer as anchors of a local news show that was all teases, all hype, no news: "Our top story tonight, 'President Assassinated'--but president of what? We'll tell you in our second half-hour."

Sustaining a cliffhangerly alarmist tone, Gasteyer asked, "Are we really safe?" and "Are safety products safe? A new report says no." Which products? Stay tuned, stay tuned, stay tuned. This is the point of much local news now: not to tell you the news, but to get you to stay tuned.

Seinfeld broke up laughing during the final sketch on the show, a wacky slapstick bit in which he was tortured as the kidnapped prisoner of goons who kept reviving him with high-tech medical gear so they could resume their pummeling and walloping. And during Colin Quinn's "Weekend Update," Seinfeld went nose-to-nose with cast member Jimmy Fallon doing an inspired impersonation of him. It would have been dueling Seinfelds except that naturally they kept agreeing with one another.

The worst thing about the new "Saturday Night Live" is not that some sketches seem pointless and fall flat. That always happened. The worst thing is that of a talented and large cast, only a few members get a chance to do much performing.

Will Ferrell, who is tall and curly-haired and plays every part the same way, was in nearly every sketch Saturday night. He was hideously inescapable. Whereas funny people like Tracy Morgan, Fallon, Gasteyer, Horatio Sanz and the brilliant impressionist-comic Darrell Hammond were hardly seen at all.

Who's producing this show--Lorne Michaels, or Will Ferrell's mother?

Hammond did a quick wicked impression of Donald Trump in the opening sketch and then seemed to go out to dinner or a movie, showing up for the curtain call and not much else.

Cheri Oteri, like Ferrell, is overused, although the two of them do work together well in sketches like their recurring "Morning Latte" bit, a parody of talk shows helmed by jabbering imbeciles.

Also disappointing was the musical guest, wheezy geezer David Bowie. That's an awfully retro way to start a "new" season of anything.

Quinn continues to shine as "Weekend Update" anchor, a segment that also serves, really, as the anchor for the whole show. Reporting on recent nuclear accidents in Japan, Quinn quoted Japanese officials: "Although the radiation was bad, it was nothing compared to the time they had two atom bombs dropped on them."

"Saturday Night Live" lives and thrives, still TV's most reliable source for topical and satirical comedy and the only one that airs "live from New York."

Never in a million years could we face a new millennium without it.