If it weren't opposite ABC's "Monday Night Football," the CBS series "Emerald Point, N.A.S." would surely be the runaway trasho hit of the season. The two-hour premiere on the network Monday night (which CBS refused to screen in advance) was a potboiler that bubbled wildly from its lurid three-minute pre-credit tease ("Emerald Point, where passions are about to explode!!!") to its obligatory but acceptable cliffhanger ending.

Dennis Weaver strides with grand imperiousness through this lavishly produced soap opera set at a fictitious naval air station. Weaver plays Thomas Mallory, an admiral who believes in the good old values but whose well-ordered world appears to be on the brink of utter devastation, whether from those nasty Cuban fighters buzzing his flyboys or from that nasty millionaire Harlan Adams (Patrick O'Neal, handily outsnarling Larry Hagman) whose greed knows no bounds, as it never does in these sorts of things, and who will stop at nothing, and so on.

The script by Richard and Esther Shapiro (who also created the campier, more foolish "Dynasty") stirred up tempests in teapot after teapot, abetted by a glittery cast of bewitching women: Susan Dey, who has the sexiest eyes in television, as Mallory's troubled and pregnant daughter Celia; Stephanie Dunnam as Kay, who gives pop the big lecture about how out-of-touch he is with his family; Doran Clark as daughter Leslie, who graduated from Annapolis in the premiere to become the seventh generation of Mallorys "to serve honorably in the United States Navy," as dad put it; Maud Adams as Maggie, whose husband has been an MIA for 10 years and is certain to come back just as her romance with the admiral gets cooking; and, most spectacularly, Sela Ward as Hillary Adams, the millionaire's nymphomaniacal, dizzy-headed, fire-breathing daughter, who doesn't even visit her husband-to-be in jail after he's tossed in on a murder charge.

If her father will stop at nothing, Hillary will stop at no one.

Andrew Stevens plays the husband, a chump of almost epic naivete', but one heckuva flyer, and Charles Frank clumps along in bland soap-opera-hero style as Celia's husband. The twists and turns were either delectably inevitable or just delectably daft, as was Weaver's how's-that-again dressing down of some carousing officers: "We are a combat-ready unit, which means just that; we are ready for combat." Got that, chief!

Still, the drama in general is on a more serious level than in the other prime-time soaps. The acting is better, the aerial footage an extremely attractive visual asset, and the depiction of conflict between civilian and military neighbors vaguely credible. CBS promoted the show as one that "will set your screen on fire!" and while that wasn't precisely the effect, "Emerald Point," directed to a fever pitch by Harry Falk, was frivolously absorbing from start to unfinished finish. 'After MASH'

"After MASH," the new CBS sequel to "M*A*S*H" that premiered on the network Monday night, opened with a lilting montage of images from the 1950s--the series is set in 1953--but unfortunately the three main characters in the show all owe their sensibilities to the sensitive '80s. They have been teleported back to the '50s to teach all those poor ignoramuses a thing or three about caring.

If the average "M*A*S*H" fan could pick three characters whose lives would be worth following after the end of the Korean War and the return home, most might pick Col. Potter (Harry Morgan), the central character here, but does anybody yearn to learn more about the schlemielish Klinger (Jamie Farr) or the insufferably goody-good Father Mulcahy (William Christopher), both of whom join the colonel in the series? Christopher plays Mulcahy like the mailman on "Mister Rogers' Neighborhood"; he's forever tooting in with glad tidings for humanity. Barry Fitzgerald must be spinning in his grave.

Unfortunately for writer-creator Larry Gelbart, decisions about who would survive "M*A*S*H" for the sequel were made by agents and network executives, not by him, and so he is pretty well stuck with these three preachy Pollyannas, who were reunited on the one-hour series premiere to work together at Gen. Pershing Veterans' Hospital in River Bend, Mo. Potter playfully refers to the place as "General General." Ho ho.

The colonel takes a $12,000-a-year job as chief of staff when he finds himself getting too antsy at home, where wife Mildred, cute as a smile button (no, cuter than a thousand smile buttons) greets him rather casually, as if he had just returned from the market. Morgan's flat, rote line readings don't help; no wonder Mildred hardly ever noticed he was gone. Ike on TV looks more passionately expressive. The program made predictable and hardly controversial statements against war and against ignoring the plight of the Korean (i.e., Vietnam) veteran, but in arch, simplistic terms.

You'd think the three old pals would have gotten together for one, deep, thoughtful, rueful reminscence about the old 4077th, but no--Col. Potter was too busy restoring Mulcahy's hearing, Mulcahy was too busy thinking up a way to get a disabled black vet to wear his artificial leg (he painted it brown) and Klinger was too busy erasing the scarlet letters VD from the records of a woman patient. Rosalind Chao, as the wife Klinger brought back from Korea, was delightful, but little used.

New foils were established in Alma Cox (Brandis Kemp), a petty bureaucrat, and Mike D'Angelo (John Chappell), a fatty bureaucrat. They won't quite do. "AfterMASH" seems to have preserved the yechy sanctimoniousness of "M*A*S*H" without finding a new equivalent to its compensating sardonic humor. River Bend came through about as profoundly and meaningfully as 79 Wistful Vista or 77 Sunset Strip. 'Dempsey'

"Dempsey" evokes a time when tales were taller, and there was great gratification in believing them, but the movie isn't quite tall enough itself. Director Gus Trikonis, cinematographer Ric Waite and art director Paul Peters were so preoccupied with creating a misty, smoky ambiance, a "McCabe and Mrs. Miller" look for their film, that it's hard to see the picture through the atmosphere.

This is a film in which ambiance almost overpowers narrative.

The three-hour CBS movie, at 8 tonight on Channel 9, has much to admire as a piece of craftsmanship. And it tells the story of the late Jack Dempsey in a fairly straightforward way, except for all the smoke and diffused lighting. Treat Williams plays the champ, who died in June at the age of 87, leaving a wealth of legends behind him and a reputation, wrote Shirley Povich at the time, as "arguably the most famous warrior in all boxing history."

What the screenplay by Edward DiLorenzo (from Dempsey's own 1977 autobiography) and the Williams performance do impart, even to a non-boxing fan--even to someone who's been left cold by boxing all his life--is what magic there is, and what particular glory, in being called "champion." More than the false, empty "Rocky" movies, which are really all about Sylvester Stallone, Underdog Movie Star, "Dempsey" captures some of the poetry that even the most sophisticated of men have long claimed to see in professional boxing.

Williams may seem physically small for a fighter, but Dempsey was no giant; he was a giant-killer. What Williams doesn't convey is a sense of swagger, of bravado. He's something of a mope, and the film too sullen, especially for its three-hour length. Among the women in Dempsey's life are Sally Kellerman, the old swooping crane herself, as a down-and-out floozie named Maxine Cates (she and Williams have a bedroom fight scene that is allowed to become ludicrous) and Victoria Tennant, of "The Winds of War," as an actress called Estelle Taylor in the film. Her character never makes much sense; she seems to be the vamp out to corrupt the champ, but this isn't really developed.

The fights are restaged effectively and lovingly, sometimes with formal titles superimposed at the bottom of the screen ("Dempsey vs. Willard, July 4, 1919") as if they were works of art. And, in fact, director Trikonis cranks things down to slo-mo so that he can very closely duplicate the famous George Bellows painting in which Firpo knocks the Manassa Mauler through the ropes and out of the ring. The effect is thrilling.

Often the characters talk as though they had learned how to talk from watching old movies, which is probably the way most of today's screenwriters get their impressions of period vernacular. Occasionally there is a sweet exchange, as when Tennant says to Williams, "You do have a way with words, don't you?" and he smiles back charmingly, "Only a few." Actors playing Damon Runyon and Babe Ruth saunter in and out of the picture, and Sam Waterston flashes an invigorating con-man's grin as Dempsey's wily manager Doc Kearns. Waterston brightens the film with almost every appearance. He is one great gleam.

The first Tunney-Dempsey match is not shown, but it is suggested Dempsey was sabotaged when someone slipped a mickey in his olive oil before the fight. Dempsey's attempt to get the title back in 1927 is the virtual climax of the film, just before a denouement that finds Dempsey being honored at a 1950 dinner and giving a moving speech about his love of the ring. Even those whose eyes glaze over when old crocks wax nostalgic about this fight or that one or the bloodiness of some poor palooka's battered face, may see what dignity and romance there was, once, to boxing, and is, probably forever, to Dempsey.