MISSISSIPPI BURNING - Two very different FBI agents, a down-home boy from the South and a Northern liberal type, descend on a Mississippi town where three civil rights workers have been brutally murdered. The action has a distinct Hollywood flavor, at times stressing fictionalized melodrama over lifelike realism. But the subject is overwhelmingly powerful, and Gene Hackman acts up a storm as the Southern investigator. Directed by Alan Parker. (Rated R) OLIVER & COMPANY - A dazzling Disney cartoon, with laugh-out-loud dialogue and eye-popping animation. Loosely based on Dickens's great ``Oliver Twist,'' the story takes place in Manhattan and stars a gang of animated animals who recall their Dickensian models in only the most charming ways. There's also a pair of loudly hissable villains. Some moments are uncomfortably reminiscent of ``Lady and the Tramp'' and ``101 Dalmatians,'' but the movie seems fresh enough overall. This Disney film could could become a classic. (Rated G) RAIN MAN - Dustin Hoffman gives a bravely obsessive performance as a mentally handicapped man traveling from Ohio to California with his brother, a fast-talking hustler who wants to cash in on an inheritance from their father. The story isn't very interesting in itself, but it has a good heart and some poignant moments as the brothers grow closer and more affectionate toward each other. Directed by Barry Levinson. (Rated R) SIERRA LEONE - Scruffy but intermittently revealing tale of a German man trying to reestablish a modest life in his own country after living and working in West Africa for several years. Uwe Schrader directed the gritty, no-frills West German production. (Not rated) THE SINGING DETECTIVE - Nearly seven hours long, this offbeat comedy-drama travels through the thoughts, dreams, fantasies, and experiences of a mystery-novel author who's recovering from a debilitating skin condition in a British hospital. Inventively directed by Jon Amiel from Dennis Potter's meandering but often ingenious script. When it was shown as a miniseries on PBS, the production carried a warning about sex scenes and language that also applies to its theatrical release. (Not rated) TORCH SONG TRILOGY - The setting is New York in the 1970s; the hero is a homosexual man who desperately seeks a lasting and loving relationship to be the center of his life. The comedy-drama is overdirected and overacted at times, but it treats its characters with respect and makes a forceful plea against antihomosexual bigotry. Directed by Paul Bogart from Harvey Fierstein's screenplay, based on his Broadway hit of the same title. (Rated R) TEQUILA SUNRISE - Trite, ham-handed crime drama about two men, a cop and a drug dealer, who've been friends since their schooldays but are now on a collision course, partly because they've fallen in love with the same woman. Slickly directed by Robert Towne from his own surprisingly clumsy screenplay. (Rated R) RATINGS: Films with ratings other than G may contain varying degrees of vulgar language, nudity, sex, and violence.