IF YOU should try to make a film so full of cloying sentimentality and embarrassing cliches, a film so poorly directed and so burdened with heavyhanded yet uninspired performances that people must turn to their television sets for intelligent entertainment, you'd probably come up with Paradise Alley.

Sylvester Stallone has become Hollywood's self-appointed poet of the simple-minded. He speaks Brooklynese, and diamonds of wisdom in the form of dese, dems and dats stream out of Cosmo, Stallone's character in Paradise Alley ("Nature's a funny thing"). Directed and written by Stallone (he even bellows the theme song), Paradise Alley invites comparisons with Rocky.

At least Rocky had some genuinely moving scenes. Stallone gave a sensitive performance and audiences responded to his character's innocence and insecurity. The whole movie seemed so full of good nature, of child-like enthusiasm, that its many weaknesses could be forgiven.

Only Stallone's mother will forgive him for Paradise Alley. The movie has all the flaws of Rocky--the truisms, the sentimentality that could make a soap-opera addict squirm--and none of its strengths. The innocence has been replaced by a blatant attempt to cash in on Rocky's success. Rocky has gone Hollywood.

Set in the Hell's Kitchen of 1946, Paradise Alley tells the story of three close-knit Italian brothers who are able to break out of New York's slums on the strength of faith, perseverance and the fortunate circumstance that one happens to be an excellent wrestler. Stallone's Cosmo is an aspiring hustler who let his hair grow and donned an earring to avoid the draft. He is supposed to be an eccentric, funny, loveable guy, with a kind heart and an abundance of home-spun wisdom. Stallone, however, fails to give his character any depth. Cosmo is an amalgamation of what Stallone thinks are appealing traits, calculated to gain our sympathy. He does not seem real. Looking into Cosmo's eyes, one only sees emptiness. His jokes are not even funny.

Cosmo convinces Victor (Lee Canalito), the brother long on muscle and short on brains, to make them some money by fighting at a wrestling joint, Paradise Alley. He is the familiar good-natured idiot, in the vein of Lenny in Steinbeck's Of Mice and Men.

The third brother, Lenny (Armand Assante), is a war hero embittered by a bad leg. He hates his job as an embalmer (why doesn't he take advantage of the numerous benefit programs for WW II vets?). Initially opposed to the idea of Victor's wrestling, Lenny succumbs to his desire for money and encourages Victor to fight. He pushes him mercilessly. It is the saintly Cosmo who, realizing the error of his own ways, tries to stop Victor from driving himself too hard.

Stallone did not give Assante any room to develop the potential conflicts within Lenny--between his desire to make money and his unwillingness to take advantage of Victor, between his need for love and his inability to accept it. Instead we see an awkward transformation of a sensitive and tortured character into an unfeeling money-grubber.

THE SUPPORTING CHARACTERS are just as poorly developed as the protagonists. There is the prostitute with a heart of gold, the tough (but tender) ten-cent-a-dance girl, and the gangster-heavy Stitch Malone (Kevin Conway) with his gang of toughs.

But we cannot care about these characters because they are mere types, devoid of life. We are supposed to be moved when we see Victor's devoted Chinese girlfriend (guess what she does for a living?) help him expand his vocabulary. We are supposed to be elated when Victor wins the final wrestling match against Freddy the Thumper, gangster Stitch Malone's obnoxious henchman, and the three brothers embrace--past disputes forgotten for the moment. What we are, however, is bored.

Perhaps Stallone foresaw some problems with such jejune characters. This would explain his painstaking efforts to inject some life into this insipid movie. He does anything to wring some emotion out of the audience, but the credibility and consistency of Paradise Alley suffers.

Take Victor's match with Freddy the Thumper, for instance. Victor goes down after 22 rounds. He only gets up because Freddy starts beating up Cosmo. This motivates him to win the match, which, we learn later, he had intended to lose because he was disturbed by the squabbling between his brothers his wrestling caused. "Why did you wait until the 22nd round if you were going to throw the match?" Cosmo asks. Victor replies, "Because I was born on the 22nd." Even Victor could not be dumb enough to get himself stomped on for 22 rounds for that reason. Stallone just wanted to show us a lot of bloody fighting.

STALLONE'S DIRECTING is as bad as his screenplay. He overuses close-ups, slow motion and freeze shots in attempting to create the dramatic tension his shallow characters and uninteresting plot fail to provide. In one scene, Victor is delivering a large block of ice to someone who lives up a long flight of stairs: close-ups of Victor's sweating face, shots of the imposing staircase, shots of Victor climbing the stairs, and so on, until he finds the customer did not want any ice. What should be drama becomes unwitting comedy.

In similar fashion, Stallone throws in some gratuitous gore. He inflicts upon us the sight of blood and mucus dripping from Freddy the Thumper's nose during an arm-wrestling match with Victor. He had to do something to liven up the long and boring scene, but this does not work.

As you watch Paradise Alley, with its tried and contrived plot and its painfully obvious and ineffective attempt to manipulate the audience's emotions, you realize that Stallone simply lacks the intelligence to make a good movie. He cannot penetrate beyond cliches.

Rocky had some appeal because of its innocent chutzpah. Anyone who had the nerve to make such a corny movie deserved to succeed. Stallone is like a child who, upon receiving a piece of candy for performing some cute and harmless stunt, promptly performs the trick all over again. Only the second time the act has no spontaneity, and becomes mildly annoying. Let's hope Stallone doesn't try it a third time.