The search for a legitimate successor to the late Bruce Lee may be nearing an unexpected happy ending.

The emergence of Jackie Chan in "The Big Brawl," an exhilarating action comedy that breathes humorous new life into the rundown martial arts genre, suggests that the time has come to retire Li, Lo, La, Lu or whatever.

Trained as an acrobat and mime during a childhood career with a theatrical troupe, Chan began starring in martial arts melodramas in his native Hong Kong two years ago. Evidently, he has already vaulted to the top of the box office heap in picturesquely titled vehicles like "Drunk Monkey in the Tiger's Eye" and "The Fearless Hyena."

Chan's first American production, "The Big Brawl" was packaged by Hong Kong movie tycoon Raymond Chow, co-produced by Fred Weintraub and written and directed by Robert Clouse, all of whom were simiarly engaged on "Enter the Dragon," Bruce Lee's splashiest hit. The Embassy Circle has been astute enough to offer the films on a double bill, making for an entertaining evening of comparative viewing.

The first Lee imitator blessed with fresh, distinctive personality resources, Chan projects a disarming, boyish affability that may eventually make him a more versatile and endearing action hero. He looks as fleet, supple and slimly muscular as Lee, and he moves with a darting comic grace that suggests an inspired synthesis of balletic traits down from both Lee and Charlie Chaplin.

Chan's funniest single physical stunt is a form of combination punch delivered upside-down: All of a sudden Chan will be standing on his hands and rapping out a tattoo of lightning-fast kicks on the noggin of some Brobdingnagian opponent, as if he were Woody Woodpecker briskly tormenting a defenseless tree trunk.

Chan appears more vulnerable and charming than Lee, who specialized in a glaring, scowling ferocity that had domineering as well as funny implications. Cast as a clean-cut, naive, fundamentlly sweet-natured college boy, Jerry Kwan, who is drawn into a national free-for-all competition, the Brawl of the Century, staged in a Texas town called Battle Creek, after defending his dad, a restaurant owner, from gangster extortionists, Chan is as friendly and eager to get along with as a Harold Lloyd character. He isn't looking for trouble, and he's more inclined to beat a tactical retreat than go on the attack or anticipate blows with Lee's stunning, overwhelming effectiveness. Still, in his elusively valiant way, Chan also prevails against brute force and intimidation.

Chan's first fight scene is delightfully conceived as an exercise in how to apply physical force while trying to avoid applying it. Learning of the shakedown attempt, Jerry confronts the gangsters in an alley behind the restaurant. Several ponderous brutes set upon him. Mr. Kwan, a peace-loving old soul, arrives on the scene and admonished Jerry to stop fighting. A dutiful if rambunctious second son (his older brother has already honored the family by becoming a doctor), Jerry tries to break away.

Caught between the angry hoods and his disapproving dad, Jerry contrives to look as if he's defending himself accidentally and apologetically. Gee, pop, his expression seems to say, can I help it if that guy ran into my elbow or those two cracked skulls when I ducked?

Chan profits from the expert support of a wily veteran actor, the splendid Mako as Jerry's martial uncle Herbert, a chiropractor who doubles as his nephew's stern, demanding instructor and occasionally goes into action himself. nMako's assurance relieves Chan of acting burdens that should be kept as light as possible in his first English language project.

Mako recalls the good-humored confidence and judiciousness projected by Takashi Shimura in his role as the leader of Kurosawa's "Seven Samurai." He and Chan also seem to have evolved a comic rapport that deserves to be sustained and extended. They're the most enjoyable fighting tandem since Burt Lancaster and Nick Cravat in "The Flame and the Arrow" and "The Crimson Pirate."

Clouse hasn't lost any of his flair for staging and editing wide-screen fight sequences. He and Lee seemed to achieve a breathtaking sense of timing: In "Enter the Dragon" Lee was often beginning retaliatory moves instants before an opponent actually became visible entering the sides of the frame. The action in "The Big Brawl" is worked out with such satisfying comic precision that even the most eccentric, Rube Goldbergian training techniques devised by Uncle Herbert turn out to stand Jerry in good stead. Setting the story in the '30s, Clouse draws on atmospheric resemblances to films like "The Sting," "Hard Times" and "Movie Movie." Herry's heroic attributes may seem more comfortable in a slightly dated context.

However, Clouse's neatest trick is to exploit the setting for anachronistic humor: neither their style of fighting nor their openly carnal attachment to Caucasian females would have been conceivable for Chinese-American good guys like Jerry and Uncle Herbert in a Hollywood movie actually made in the '30s. Clouse contrives to make amends for some old racial taboos.

There are a couple of unaccountable slip-ups in the plotting. Jerry is coerced into competing in the Brawl of the Century when a gangster gambler played by Jose Ferrer kidnaps his brother's fiancee and holds her hostage. At the conclusion Ferrer is seen offering assurances that the girl is safe and sound, but it would be preferable to see her safely restored to the Kwan family.

Clouse introduces a promising character at the time of the kidnapping and then fails to follow through. The hero is supposed to bring the fiancee' back to Chicago from her home in San Francisco. When she's snatched by Ferrer's agents, he reluctantly agrees to accept an imposter, a gum-chewing tart played by Joycelyne Lew, (Luckily, brother and fiancee have never met; the engagement has been arranged by their parents). The idea of passing off this disreputable but apparently likable tootsie on his upstanding dad and older brother suggests hilarious possibilities, but Clouse seems to forget he's got a funny subplot going for him.

After the returns from "The Big Brawl" are in, Clouse and his associates should have plenty of opportunities to fine-tune the cinematic adventures of Jackie Chan.