Harvey Korman and Buddy Hackett are nearly sensational as Abbott and Costello in "Bud and Lou," a two-hour NBC movie about the top bananas of the 1940s.

The film, at 9 tonight at Channel 4, is inadequate for its subjects and its two stars, but touching and persuasive anyway, because the life stories it tells, in snippets and vignettes, are the stuff American dreams are made of and crushed by. Abbott and Costello made the traditional meteoric rise and subsequent meteoric fall; their slapstick antics (on stage, screen and radio were paralleled by extremes of misfortune and tragedy in their real lives.

Abbott, the tall and moderately dashing straight man, suffered from bouts of epilepsy, alcoholism, and chronic fear of success. Costello, the pained little fat man who was told by hs manager, correctly, that he had "pathos," appears determined to use his fame and money as a weapon. There is something heroic, in an against the world that earlier ignored oddball way, about his venzefulness.

On the night of his comeback to radio after months of illness, Costello learned that his 1-year-old son had drowned in the status symbol backyard pool that had been built with his share of the team's fabulous earnings. Costello went on and did the broadeast as scheduled, it was as if his life as a clown had been written by a morbid French poet. He was a proletarian poor Pierot who never got the girl in his films and whose comedy is underestimated by everyone but the millions of kids in each new generation who make him an idol all over again when they see Abbott and Costello movies on television.

Korman suggests Abbott handsomely enough, but it is Hackett who sets his socks off in the more demonstrative role of Costello, a broad, emphatic, turbulent performance that seems an expression of heartfelt empathy for a fellow baggy-pants Hamlet. The restaging of classic Abbott and Costello routines - inescapably including, "Who's on First" - looks perfunctory if authentic, but the backstage tribulations are handled with care and performed affectingly.

Much has been omitted from Abbott and Costello's lives. Writer George Lefferts, working from a Bob Thomas book, dropped such pivotal characters as John Grant, who wrote much of their material, and Bud Abbott's wife. The physical nature of their comedy is ignored, and Abbott's slaps to Costello's face are referred to parenthetically. Missing, too, is the joy that must have come with triumph, when this pair of Everymen struck it so big in Hollywood that they remained among the top 10 box office attractions throughout the decade.

They were sunshine boys.

Lefferts and director Robert C. Thompson wee more adept at capturing the cruelty of decline and fall - the death of Costello's son, the team's devastating persecution by the IRS, and the final bitterness of their separation.

Where the treatment is shallo or negligent, the actors compensate with a compassionate intensity. Hackett's Costello is emotionally spectacular; with the "baaaaaaaad boy" of the screen sometimes playing the bad boy off the screen, conditioned by his youth and years of struggle to expect conspiracies against his well-being. There is a greater and still more poignant story to the lives of Abbott and Costello than "Bud and Lou" tells, but the film succeeds as a crudely eloquent aside. In addition, it seems an earnest act of love, homage and forgiveness.