Saturday night's alright for fightin' ...and fantasy...and fun, too, as several promising shows land here

Saturday, the night of the week with the smallest TV audience, may also have the highest concentration of promising new shows: three out of four, with a hideous Bo Derek drama as counterweight. At least two of the new shows are so good - fun one-hour shows too lighthearted to be called "dramas" - that you want to root for the ratings fates to be kind to them. Picks to click Could "Martial Law" have arrived at a better moment? This campy, high-kicking romp starring Hong Kong film star Sammo Hung follows by one week the smash box-office opening of Jackie Chan's new movie. In spirit and in personnel, "Martial Law" is the Chan genre of action film brought to the small screen. It debuts at 8 tonight on Channel 5. Hung, a bear of a man at about 5-foot-7 and 220 pounds, dispenses justice to the bad guys in L.A. with his feet and any implement close at hand (5-gallon bucket, chalkboard eraser etc.). He's helped out by a latter-day Mod Squad - his female partner even looks like Peggy Lipton - but the show really revolves around Hung, who despite his poor command of the English language lights up every scene he's in. After you've thrilled to Sammo, chill out with the delightful new "Cupid" at 9 on Channel 9. Jeremy Piven ("Ellen") is convinced he is the 3,000-year-old god of love; Paula Marshall ("Spin City"), a Chicago shrink who also advises the young and lovelorn, thinks he's out of his mind. His fanaticism, her skepticism and some terrific writing from newcomer Rob Thomas (who wrote the infamous teacher-seduction episode of "Dawson's Creek") make for one of the brightest new hours on TV this fall. As a non-couple, these two certainly have a lot more going for them than that overhyped "Will & Grace" - well, except for the time slot. What else is new The remake of "Fantasy Island," a show that aired on this night 20 years ago, debuts at 8 on Channel 9 with a new Mr. Roarke, played by Malcolm McDowell. In the first episode, he symbolically dons a black coat and orders someone to destroy all the white coats. It's one of several signs that this oddball with a cruel streak won't be anything like Ricardo Montalban. With the aid of special effects and his staff - played by the alluring Madchen Amick, debonair Edward Hibbert from "Frasier" and buffoony Louis Lombardi - Roarke concocts a series of bizarre wish fulfillments for his guests. There's also a sort of phantom tollbooth the guests must pass through, an inauspicious looking travel agency run by a twinkly old man (Fyvush Finkel) who in his own way is as weird as Roarke. Whether viewers will warm to the sometimes cold-hearted "Fantasy Island" remains to be seen. But there's little doubt what will happen to "Wind on Water," the fall's undisputably dead-on-arrival show, when it finally does arrive Oct. 17. Bo Derek runs a ranch on Hawaii that teeters on bankruptcy. She has two sons who can't get enough of extreme sports, which may explain why the ranch is in trouble (not to mention this show). Surfin' turf You've heard that NBC agreed to shell out $ 13 million an episode for "ER. " But the networks aren't profligate every night of the week, especially Saturdays. One way they can control costs is by owning a chunk of the shows they put on the air. By agreeing to share in a show's financial risk, the networks can help reduce the amount they pay to put that show on the air. And should it ever be syndicated in reruns - as "Walker: Texas Ranger" and "Cops" are - the network shares in the proceeds. So it's no wonder that, on a low-rated night like Saturday, when the need to keep costs down is imperative, the networks have ownership shares in eight of the 11 prime-time shows. Not that there isn't a downside. For instance, NBC owns "Wind on Water" outright. If you ask me, they can have it.