Madison Avenue keeps making great commercials, and Hollywood keeps making terrible television shows that can't begin to compete with them. A solution of sorts has been found: "Television's Greatest Commercials," an NBC special at 10 tonight on Channel 4--the first program on commercial network television to take a program-length look at network television commercials.

The special is not as comprehensive as "We'll Be Right Back," a 90-minute special made for Showtime, the national pay cable network, and shown last year. However, the quality of sappy patter on the NBC show is decidedly superior; Ed McMahon and Tim Conway cohost the program with brisk and ingratiating geniality. Ed's putting on weight again--this has us worried--but he remains one of the more commanding straight men in the history of TV comedy.

Producers Joie Albrecht and Scott Garen organized the commercial excerpts into thematic groups. Few commercials are seen full-length, which is a problem. Sometimes you can't tell what the commercial is a commercial for. And if you're going to call your commercials "Television's Greatest," it's pretty inexcusable not to include the Alka-Seltzer classic, "That's a Spicey Meat Ball," which was in the Showtime show. But the producers included so many other Alka-Seltzer spots they were afraid their program would become overly alkaline.

Each segment is a medley of word and picture images that over the years have reflected and helped shape the culture. A segment on symptoms, for instance, tumbles out like this: "Aw-oh! Foot odor!" "Hey, Dad, the house smells funny!" "I can't believe I ate the WHOLE thing." "Indi-gess-tion." "Control yourself; don't take it out on the children. Sure, you have a headache . . . "

Another sequence concentrates on creatures great and small, from the smirky and supericilious Morris to singing felines ("Meow meow meow meow," and so on) to Alka-Seltzer's famous talking stomach (an R.O. Blechman cartoon, with a voice that sounds like Gene Wilder's) to regional ads Jim Henson's Muppets did, long before worldwide fame, for Wilkins Coffee. Ed shows a tape of that ill-fated Alpo spot he did on a "Tonight Show," when the dog wouldn't eat the food, and so Johnny Carson, on all fours, filled in.

Portrayals of women and men in commercials show how the roles have changed over the years, or how Madison Avenue has perceived the change, with the American woman's image undergoing far greater renovation--starting with the traditional homemaker spots ("You load 16 tons of knotted-up clothes . . . ") and leaping forward to the downright upright, assertive sexpot of today's ads: "Steven? Hi, this is Carol. Are you busy tonight?" Presumably, this is progress. Now we have women propositioning men on airplanes by stealing their sunglasses from them! The very idea!

The program is most inadequate in sequences on special effects and on sex as a selling tool. Any child will be able to think of innumerable special effects more dazzling than the ones shown (remember the hand that picked a building up out of its moorings for some computer company?), and the sexy spots aren't really up-to-date, what with all those hotsy-totsy New-Wavey ads for perfumes and colognes and what-not flooding the air waves.

Briefly glimpsed nobodies who appeared in commercials and later became varying degrees of somebodies include Marsha Mason, Tom Selleck (slapping Chaz on his primordially hairy chest), Susan Anton (doing her fetchingly provocative locker room seduction--quickly yanked from the air--for Muriel cigars), Louise Lasser and John Travolta. There also is a segment on stars commercials created: Tony the Tiger, Mrs. Olson, Mr. Whipple, Josephine the Plumber, the Maytag repairman, and that boring klutz of a clown, Ronald McDonald.

Watching some of the black-and-white ghosts from the past is like looking at home movies of one's youth. And a sequence on the use of sentimentality in ads shows what a bullseye can be hit when Mad Ave aims for the heart (though the best of them all, Kodak's vintage "Turn Around" spot, is only heard, not seen). The show ends with a finale that is a finale, Stan Freberg's hilarious Busby Berkeley production number, starring Ann Miller, for Great American Soups.

Superficial, scattershot and incomplete though it is as a survey, NBC's hour of commercials could prove to be the most entertaining show on television this week, and the most entertaining show on NBC this year.