LOS ANGELES (Zap2it.com) From "The Twilight Zone" to "Star Trek" to "The X-Files" to "Lost," science fiction, fantasy and horror shows have captivated fans, sometimes holding them in thrall for years or even decades after they end.

Despite this, so-called "genre" shows and ratings-dependent network television have had an uneasy partnership. If one scans through the season-by-season top 30 show listings in "The Complete Directory to Prime Time Network and Cable TV Shows (1946-Present)," by Tim Brooks and Earle Marsh, only two genre dramas appear in the coveted Top 20.

The first is NBC’s "Project UFO," producer Jack Webb’s 1978-79 midseason procedural drama about Air Force officers investigating UFO sightings as part of Project Blue Book. Although it finished its debut run at No. 19, it only earned one more season.

Then in the fall of 1993, FOX premiered "The X-Files," a procedural drama about FBI agents investigating the paranormal, in particular UFOs and aliens. It took until the 1997-98 season to crack the Top 20, coming in at 19, but it managed to last for nine seasons, garnering critical acclaim and becoming a pop-culture phenomenon.

Unfortunately, no genre show since has duplicated the achievement of "X" as both an unqualified critical and commercial success. "Buffy the Vampire Slayer," which did five seasons on The WB Network and two on UPN starting in 1997, was a critical darling but a commercial hit only by weblet standards. The same is true of the witch drama "Charmed," whose ratings were enough to earn it an eighth season on The WB but which never would have survived on ABC, CBS, NBC or FOX.

In the recently concluded 2004-05 season, glutted with the success of reality shows and such down-to-earth procedural franchises as "CSI" and "Law & Order," most of the broadcast nets shied away from new genre shows. Ultimately, it was struggling, downtrodden ABC that rolled the dice on a genre concept.

The result was "Lost," executive produced by J.J. Abrams (ABC’s "Alias") and Damon Lindelof, a kinetic mix of "Robinson Crusoe," "The Island of Dr. Moreau," "Survivor" and hints of the supernatural. It became a pop-culture smash and finished its first season ranked No. 14 in total viewers. This convoluted, roller-coaster-ride saga of plane-crash survivors on a seriously bizarre tropical island helped to put ABC back in business.

Then as if by magic, genre pilots popped up on the nets’ schedules for this coming fall.

ABC has two: "Invasion," with executive producer Shaun Cassidy ("American Gothic"), is a Wednesday companion to "Lost" that looks at an alien invasion in a hurricane-ravaged Florida town. "The Night Stalker," with executive producer Frank Spotnitz ("The X-Files"), is a reimagining of the 1970s ABC series about a reporter investigating the paranormal, which will air after "Alias" on Thursdays.

CBS has two airing back to back on Fridays: "Ghost Whisperer," about a pretty newlywed who can commune with the dead, and "Threshold," with executive producers Brannon Braga ("Star Trek: Enterprise") and David Goyer ("Blade"), a sleek thriller about a team of experts dealing with an alien threat.

NBC has one: "Fathom," created by twins Josh and Jonas Pate ("G vs. E") and airing Mondays, about a possibly menacing new life form that suddenly appears in the world’s oceans.

And The WB has one: "Supernatural," from executive producer McG ("Fastlane"), about two brothers seeking their missing father while investigating supernatural mysteries on America’s back roads.

"’Lost’ is certainly an influence on some of the development," says Javier Grillo-Marxuach ("Boomtown," "Jake 2.0"), a supervising producer on the show, "but I think people are still hunting for the ’X-Files’ grail, even though that show has been canceled for years now."

So what made "X" stand out? "My theory," Spotnitz says, "and I could be wrong, is that on network television, you start from reality. The premise needs to feel credible, like it could be happening in the world we all live in. Without that, there are just too many people in the large, large tent that network television represents who aren’t even willing to give it a try.

"You need to make it feel like a show they would watch, a mystery show, a police show, then introduce the far-out element."

As did "The X-Files," Grillo-Marxuach thinks "Lost" may be helping to change the perception that genre shows aren’t for grown-ups.

"If we have helped genre television get to the adult table, that’s great," he says. "Genre television has done a lot of growing up in the last few years. There’s a willingness on the part of writers to approach it the way writers of literary science fiction do, which is to make it about things that are important to the audience, which is character and all that, and not think of it merely as a vessel for eye candy and cool stuff."

Fans may have enjoyed the alien-conspiracy subplot on "X-Files," but they loved Mulder and Scully. On "Lost," if we ever see the invisible menace, would we care if our beloved Jack, Sawyer, Hurley, Kate, Locke and the rest weren’t in mortal danger? Special effects can’t compensate for cardboard characters or hackneyed plots.

"At the end of the day," Grillo-Marxuach says, "it’s not whether you’re doing reality, genre or procedural, it’s whether you’re doing it really well and the audience responds to it."