“MASTERPIECE THEATRE: FIFTEEN YEARS,” Sunday, 8 p.m....

“MASTERPIECE THEATRE: FIFTEEN YEARS,” Sunday, 8 p.m. (50); 9 p.m. (28)(15)--All right, so they weren’t all masterpieces. Even Alistair Cooke admits that.

Yet the vast majority of 82 “Masterpiece Theatre” productions (with more coming later this season) really have been swell, TV dressed up in its stunning Sunday best.

No continuing series deserves standing applause more than this one. And that is exactly what PBS is planning Sunday when it celebrates the 15th birthday of British-bred “Masterpiece Theatre,” one of American TV’s longest-running and most revered institutions.

Cooke, the urbane host whose understated commentaries have become the signature for “Masterpiece Theatre,” will be there, along with a number of other familiar faces ranging from Jean Marsh (“Upstairs, Downstairs”) to Susan Wooldridge and Tim Pigott-Smith (“The Jewel in the Crown”). And there also will be lots of clips on the two-hour program.

Like any 15-year-old, “Masterpiece Theatre” has some zits. Far and away, though, it’s been a welcome letter from Britain, offering viewers an eyeful of foreign TV and money-strapped PBS the chance to air the kind of upper-crust drama that it could not afford to have produced in the United States.

The irony is that we are watching the best of British TV on PBS while lower-crust American TV still is sizzling in Britain. “Dallas” and “Dynasty” may have suffered a slight charisma lapse here, for example, but they continue to be enormously popular in Britain. “Masterpiece Theatre” notwithstanding, the TV tastes of the average Britisher are no loftier than those of his American counterpart.

Both nations have TV strengths. I’ve never seen anything produced by the British that matched NBC’s “The Cosby Show” nor the hip whimsy of ABC’s “Moonlighting.” And in any global duel of TV comics, my money goes on David Letterman.

Yet the British, banking on their astounding quality control and reservoir of dependable character actors, turn out short-run serial dramas by the oodles that leave ours standing in the dust.

An American “Masterpiece Theatre”? You’d be hard pressed to turn up more than a handful of American miniseries from the last 15 years that would be worthy of inclusion. You might start off on a moderately high note with a few middlebrows, but it wouldn’t be long before you’d be scraping “Hollywood Wives” and “Harem” off the bottom of the barrel.

And who would be our Alistair Cooke? Aaron Spelling?

The real “Masterpiece Theatre,” on the other hand, has yielded extraordinary highs, stories so richly detailed and well acted that you anxiously await second and third helpings.

Happy birthday.