Sitcoms: TV doesn't know whether to laugh or cry; `Delicate art form' ails in new era of reality TV, but some insist on revival.(Special Report: TV's Upfront)

Byline: T.L. STANLEY

It's a scenario that plays itself out dozens of times on any given night during network TV sitcoms. It goes like this: setup, setup, joke, laugh. Then, on the really elaborate goofs, it's setup, setup, joke, laugh, plus wacky reaction shots from each of the characters. Bonus points if there's an adorable and precocious kid who can roll his eyes at just the right moment.

So how come no one at home is guffawing nearly as hard as the (heavily sweetened) laugh track?

Network executives, as they head into this year's upfront ad-selling spree, have been asking the same question, along with deeper ones about the once-brilliant-but-now-struggling genre. What in the world has happened to the situation comedy, and can it be fixed?

With two of the most successful, long-running half-hour comedies-"Friends'' and "Frasier,'' both fixtures on General Electric Co.'s NBC-leaving the air this season, there's no heir apparent to draw a broad advertiser-coveted 18-to-49-year-old audience and feed the money-making syndication pipeline. "Everybody Loves Raymond'' may return next fall for a ninth outing on Viacom's CBS but likely just for one …