"The Greatest," the film about the life of Muhammad Ali which opened yesterday at area theaters starring the champ as himself, doesn't quite live up to the superlatives of its title, despite some tender scenes and at times convincing acting by Ali. But it scores well as a fascinating trip back into some recent social history and reminds us that beyond the stunning athletic achievement, the heavyweight champion of the world had another important role.

As a film, "The Greatest" grows progressively glib, drowning us in the public melodrama while offering only tantalizing gulps of the private Ali - the doubts, the fears, the influences that shaped his life. And its about ending, with Ali on the edge of triumph, is unsatisfying to an audience well aware of Ali's roller coaster present.

Ring Lardner Jr.'s screenplay traces Ali's life through his small-city beginnings, 1960 Olympic gold medal, the influence (of Malcolm X and his conversion to the Muslim faith, his swift rise to the championship, his fall during the Vietnam War and the climb back - with the junk fights, taunting crowds, recriminations by his manager and doctor - and the pressure to retire.

But the motivation behind the public Ali isn't probed. All we get of Ali's early life are his brushes with bias. Louisville-style, and a scene in church where a white-robed choir is chanting beneath a white Jesus (zoom in for a close shot.) What gave this lad, clearly destined to be different, that uncanny assurance - if indeed it was always assurance? When he discovers that his Olympic gold makes him still only a boy in his hometown and flings it into the river, crying, "This thing is a phony, gold-plated . . . it ain't worth a damn," did he in this symbolic act toss away his naivette about racism? Was that empty space just waiting for Malcom X to fill it? The clues on screen are few.

Ali's charisma and personal charm carry us over some cursory scenes, but his conversion still seems unconvincingly easy. Didn't he grapple more with the implications of his decision, particularly since most black Americans, though sympathetic to Malcom X, weren't in tact Muslims?

As social history, "The Greatest" reminds us of how solidly Ali was in sync with his times. It is his involvement with the Vietnam War, in fact, that gives him deep meaning in American history. Ali rasped, "The Vict Cong never called me no nigger . . . they your enemy, not mine," well before the national protest ultimately halted the war. It's only implied that his words initially revived the deep seated American fear of black loyalty in time of war.

A quarter-century ago, Paul Robeson stood in Paris' Salle Pleyel at the height of the Cold War and said it was "unthinkable" to him that black Americans could "take up arms in the name of an Eastland . . ." The sentiment meant artistic and political death for that performer/activist.

Twenty-two years later, on April 4, 1967, Dr. Martin Luther King Jr. became the most prominent American to denounce U.S. involvement in Vietnam when he labeled the U.S. "the greatest purveyor of violence in the world today," charged President Johnson with lying about Hanoi's peace overtures and urged Americans to become conscientuous objectors. A year later, he was assassinated.

It was in the same period that Ali resisted the draft, had his title snatched away and was forced into 3 1/2 years of exile. In real life, he used television news to take his message to a public whose legacy of the '60s was a distrust of the government and a growing world sophistication. He helped educate people because his simple and direct approach could be understood emotionally by millions. (As Ali said in explaining why he failed the army intelligence test, "I said I was the greatest, not the smartest.")

The film's point of view on Ali's treatment by his own government is clear: that stripping him of his title, his passport and his ability to earn a living was a calculated attempt at emasculation. But his pride remained intact, and he was ready for a comeback when the Supreme Court ruled that his religious beliefs were sincreely held and restored his passport. A few years later, Ali could be invited to the White House, among the chosen few to greet the Wueen of England to ultimate symbol of Western Society.

This movie does some interesting things, too, as black cinema, where the past half-century has seen the march from black invisibility to systematic dehumanization to ebony saint to superspade to subtle racism to . . . what?

Ali's woman, for instance, is outside the dominant pattern of the black female characters of the late '60s and '70s, who were beautiful (by white standards) but supersexed and at best amoral.Some of the tenderest scenes in "The Greatest" are between Ali and Annazetta Chase, who plays his second wife, Belinda.

And Ali's touting of his beauty is different from that of the Calvin Lockhart character who begins the 1972 "blaxploitation" film, "Melinda," by telling his mirror. "God I'm a lovely mother . . .," and climaxes it by a stacatto smashing in of the white villain's head. Ali is a hero whose bombastic buffoonery is part of a carefully calculated design to captivate the public and the media, and films like "Melinda" are now largely passe.

"The Greatest" is the sort of movie that hasn't come along too often - lots of action but little violence (beyond the ring) or explicit sex. In the rocky progression of black film it shows another facet of the vitality and variety of black life.

With a supporting cast that includes Ernest Borgnine (as the fighter's long-time trainer Angelo Dundee), Lloyd Haves and John Marley and special appearances by James Earl Jones, Paul Winfield and Dina Merrill, Ali turns in a respectable, even zesty performance in this screen debut.

It's been hinted that Ali in the tradition of Jim Brown, finally will make good on his on-again, off-again decision to retire, if he can make it big as an actor. It's a legitimate tradition, even if Brown's bare-chested roles were played sometimes as if he was coached by a robot. It remains to be seen of course whether Ali can create a believable portrayal of another character.