Television: In the inexact world of programming, potential hits can die on the vine.

NBC executives didn’t care for “ER� when they first saw it. Test audiences hated “Seinfeld.� ABC passed on “The Cosby Show,� and Fox executives wanted a then-unknown actress, Gillian Anderson, exiled from “The X-Files.�

Despite such hurdles, those programs survived television’s screening process, eventually gaining public adulation and riches of lottery-winning scale.

What the public hasn’t seen are “Dear Diary,� “The Doyles� or “Moe’s World�--proposed series that generated positive buzz within Hollywood circles but never received the production go-ahead that would have catapulted them from screening rooms into living rooms.

The process of developing new programs is currently building toward the frenzied period in May when programmers unveil schedules for next fall. Between them, the six broadcast networks will order more than 120 series prototypes, or pilots, with no more than 4 in 10 destined to become series.

Critics often decry the quality of shows served up each September, and even those within the industry joke about something in the jet stream that ruins new programs between Los Angeles (where they’re initially screened for executives) and New York, where schedules are unveiled to media buyers.

What’s most vexing to some involved, however, is good stuff that doesn’t make the cut, because of factors that range from industry politics to test-audience responses or assumptions that a genre has fallen out of public favor.

In the sifting, a few potential gems can slide through the cracks--an occurrence especially frustrating to the producers of such shows, who, unlike in the movie business, have little recourse in showcasing the remnants of rejected series.

Joseph Stern, whose credits include “Law & Order,� is still smarting over “The Doyles�--an understated ABC drama about working-class Irish Catholic parents struggling to raise four young daughters.

“I really think the ball was dropped here, that this was a phenomenal show,� said Stern, who produced the project last year with Barbara Hall. “This was the best piece of television I had been involved with since ‘Law & Order.’ It’s a mystery to me why it didn’t go on.�

ABC declined comment, but sources say the show was perceived as being too soft, especially after the network had just struggled unsuccessfully to lure viewers to another family drama, “Second Noah.�

When ABC passed on his 1996 pilot “Dear Diary,� producer David Frankel had it exhibited in theaters just long enough to qualify the half-hour program--which starred “Cheers’ � Bebe Neuwirth--for Academy Award consideration. In a note of considerable irony, a production discarded by ABC proceeded to win last year’s Oscar as best live-action short film.

Frankel knew “Dear Diary�--an expensive project shot without an audience that had the main character frequently narrating her thoughts--would present executives with a curve ball in terms of scheduling.

“One of the biggest problems when you have a show that’s distinctive is what do you put it with--what do you put before it and what do you put after it? I think that’s one reason distinctive hours work better than distinctive half-hours,� said Frankel, noting that an offbeat show like Fox’s “Ally McBeal� has an advantage in that regard.

Indeed, Frankel faced a similar problem with a show of his that did get ordered, “Grapevine.� Even with positive reviews, the 1992 comedy anthology had a hard time retaining viewers paired with the more conventional “Murphy Brown.�

Programs that go unseen by the public can nevertheless provide a career-enhancing lift to the creators or stars within the entertainment industry.

That proved to be the case with “Moe’s World,� a 1991 pilot told through the eyes of a dead, 12-year-old African American boy who watches over his old neighborhood. Executives at New World Television were so enthralled with the pilot that, unbeknownst to ABC, they sought to influence waffling network officials by giving the show to Times critic Howard Rosenberg. He decided to write a column about it, calling the show “irresistible,� and adding, “If ever something merited room in prime time, this little beauty is it.�

Though the network couldn’t be persuaded, writer-producer-director Kevin Rodney Sullivan said the pilot’s reputation helped open doors for him.

“ ‘Moe’s World’ was a very nontraditional piece,� said Sullivan, who’s currently directing Angela Bassett and Whoopi Goldberg in the feature “How Stella Got Her Groove Back,� which will be released this summer.

“To get an opportunity to realize that was great for me as a filmmaker in terms of developing my craft. . . . That was a big rite of passage for me. People knew me as a writer but not as a director.�

In similar fashion, CBS chose not to try to acquire “The Doyles,� instead reuniting its star, Jason Beghe (“G.I. Jane�), with director Jim Haymon and writer Joanne Waters in developing a new program that’s now a candidate for next season.

Competing networks do occasionally pick up pilot castaways, as the fledgling UPN did with “Moesha,� its most popular comedy, which was initially developed for CBS. New series buyers, in fact, have created outlets for shows that might otherwise have died on the vine, such as “The High Life�--another CBS pilot, set in the 1950s, which ended up getting a shot (revised to include saltier language) on HBO.

Even seven years later, Sullivan indicated that executives still periodically express interest in “Moe’s World,� adding that it is “not outside the realm of possibility� that he might revisit the concept. Of course, he’d be hard-pressed to reassemble the cast, which included feature star Jada Pinkett Smith, S. Epatha Merkerson (“Law & Order�), Tisha Campbell (“Martin�), Carl Lumbly (“The Wedding�) and Bill Cobbs (“The Gregory Hines Show�).

Frankel remains philosophical about “Dear Diary,� noting that network television doesn’t have the luxury of producing the equivalent of art-house films. (A rejected ABC pilot titled “Where’s Marlowe,� in fact, is currently being expanded by its producers into a low-budget feature.)

“Deep in the hearts of the best television executives, there is a desire to embrace new things, but it’s hard if they don’t see that potential [to get big ratings],� Frankel said.

In Stern’s view, however, a medium suffering from a dearth of great shows needs to put on as many as can be found. Struggling networks, he added, have more cause and license to gamble on quality programs that may possess uncertain commercial appeal.

“I use a football analogy: If you’re the Dallas Cowboys, you draft for position,� Stern said. “If you’re an expansion team, you take the best athletes.�

Frankel also chose a sports metaphor to characterize the vagaries of series development. “It’s like watching the Olympics,� he said. “Sometimes you get the gold, sometimes you don’t.�