As America goes, so goes prime-time television....

As America goes, so goes prime-time television. Or is it the other way around?

Television is 50 years old this month (based on the first telecast from the 1939 World’s Fair), but it is difficult to say whether it has truly matured.

NBC, which won the just-ended prime-time season for the fourth year in a row, did so by the largest margin of any network in 32 years. It did so in the grand tradition of prime-time programming: safe TV.

More than moving ahead, prime-time entertainment has spent the past 50 years retracing its steps.

A quick browse down the top 10 list of decades past proves that though social mores may change, TV formulas rarely, if ever, do.

In the 1988-89 season, eight out of the top 10 shows were sitcoms, with “The Cosby Show,” “Roseanne” and “A Different World” at the head of the class. The two shows that were not sitcoms were “60 Minutes” and “Murder, She Wrote.”

Ten years ago, nine of the top 10 shows on the air were sitcoms.

In the 1978-79 season, “Laverne & Shirley” was No. 1, followed by “Three’s Company,” “Mork & Mindy,” “Happy Days” and “Angie.” Only CBS’ prestigious news magazine “60 Minutes,” the No. 6 show that season, was going for something other than laughs.

Ten years before that, six of the top 10 shows were sitcoms, and two others, “The Dean Martin Show” and “Rowan & Martin’s Laugh-In,” were comedy-based.

Thirty years ago, eight of the top 10 shows were Western-based, with the classic “Gun-smoke” outdrawing the competition, followed by “Wagon Train,” “Have Gun Will Travel” and “The Rifleman.” Only “The Danny Thomas Show” and “I’ve Got a Secret” broke the trend.

See a pattern here?

Obviously, television is not a medium that likes to take chances.

Consider the shows in recent years that have tried to break the mold. Most that challenged convention have been outright ratings failures.

So-called “dramedies,” such as the luminous “Frank’s Place” on CBS and NBC’s “The Days and Nights of Molly Dodd,” now running on the cable network Lifetime, failed because viewers--and, perhaps just as important, network presidents--did not know what to make of them.

Ensemble shows such as NBC’s “St. Elsewhere” and “Hill Street Blues” took a lot of time and network patience (always on short supply) to make it, but even then they were critical, rather than ratings, success stories. ABC’s “Max Headroom” got far more press than viewers and was canceled. The network’s much-talked about “thirty-something” ended up fortysomething in this season’s year-end ratings.

TV viewers find safety in numbers when it comes to innovation.

In truth, outside of news and information and so-called reality-based programs, there has only been a handful of successful prime-time formulas in 50 years of network television. There is the situation comedy, the soap opera, the variety show and the game show. Then there are the various versions of the TV drama: the cop show, the medical show and the Western.

In some cases, such as the variety show, the best appears to be behind us.

It is difficult to imagine a renaissance of variety shows (remember ABC’s disastrous “Dolly” in 1987) that would result in a modern-day version of “The Ed Sullivan Show.” Variety shows, in the post-VCR world, are about as exciting as black-and-white television.

The Western, long considered a dead horse, may well be trotted out again, thanks to the success of CBS’ “Lonesome Dove” miniseries, though the network’s “Paradise” needed a posse to find viewers.

But in other cases, TV seems to be on the verge of something new, especially in the world of situation comedies.

TV parents, be they Donna Reed, Fred MacMurray, Danny Thomas or Andy Griffith, have at some point counseled their kids through growing pains, taught them about responsibility and prepared them for life outside the home (though they never seemed to leave home).

But social mores and problems have changed enough that sitcoms in recent years have often become important informational forums.

CBS’ “Designing Women” did an episode on AIDS, ABC’s “Growing Pains” has tackled drug and alcohol abuse, and “Roseanne” explored menstruation. Certainly, that is a far cry from anything the public was prepared to see in an episode of “I Love Lucy” or “Make Room for Daddy.”

Yet the need for safe, nostalgic shows remains. “Perry Mason” is alive and well in TV movie form on NBC. ABC brought back “Mission: Impossible” this year. Reunions--from “Dobie Gillis” to “Eight Is Enough” have become commonplace. Some TV characters--much to their detriment--never really left (such is the case with Jerry “Leave It to Beaver” Mathers). And, of course, dozens of shows live on in syndication.

That, too, is part of television’s love affair with itself, a need to return to better times, even if it is only briefly.

But TV only does what it is told; if we love “Dirty Dancing” the movie, we will have “Dirty Dancing” the series. Which leads one to the conclusion that if prime-time TV leaves something to be desired, the fault lies not in our network stars but in ourselves.