BABY BOOM - When a little girl drops unexpectedly into her life, an ambitious businesswoman tries to combine child-raising and careerism. But her values soon tilt toward the family end of the scale, to the consternation of her executive cronies. The movie's portrait of yuppie life is wickedly hilarious, and Diane Keaton gives her funniest, most intelligent, most lovable performance in years. The screenplay loses its energy when our heroine moves from Manhattan to Vermont, though, and the filmmakers have an annoying habit of showing most non-New Yorkers as hayseeds and weirdos. Directed by Charles Shyer. (Rated PG) BARFLY - The life and times of an alcoholic author, directed by Barbet Schroeder from a smirking, superficial, and self-aggrandizing Charles Bukowski screenplay. Faye Dunaway gives one of the year's most fully realized performances as the hero's girlfriend. Mickey Rourke woefully miscalculates his role, though. Is that a W.C. Fields imitation he's doing? (Rated R) DANCERS - While directing a film version of ``Giselle,'' a ballet star gets into an ambiguous relationship with a young woman who's dancing in the production. The ballet scenes are lovely, the story is trite, the filmmaking is terribly ragged. Directed by dance-lover Herbert Ross, far below his best form. (Rated PG) HAIL! HAIL! ROCK'N'ROLL - A portrait of rock-music pioneer Chuck Berry, with concert scenes featuring a band organized by Rolling Stones guitarist Keith Richards. Berry talks at length about his life and career, although he won't discuss some issues, including time he spent in prison years ago. Other people interviewed, such as rock stars Bo Diddley and Little Richard, offer valuable insights into the roots of Berry's style and the early rock scene as a whole. Taylor Hackford, best known as a fiction filmmaker, directed the overlong but marvelously energetic picture. (Rated PG) NEAR DARK - A sort of western about modern-day vampires. Directed by Kathryn Bigelow with lots of dull spots, a few effectively intense moments, and as much gore as the monster genre usually calls for nowadays. (Rated R) SURRENDER - Fed up with high alimony and ``palimony'' payments, a successful author tests the sincerity of his new girlfriend by pretending he's poor. The comedy is as creaky as that ancient plot gimmick, but Michael Caine and Sally Field are clever enough to milk a few good laughs from the situation. Written and directed by Jerry Belson. (Rated PG) THE WHALES OF AUGUST - Lillian Gish and Bette Davis are radiant as two elderly sisters who aren't sure whether it's a good idea to spend the rest of their lives together. Other assets are a strong supporting cast, headed by Vincent Price and Ann Sothern, and gorgeous shots of the New England coast, where the drama takes place. David Berry's screenplay is not correspondingly stirring or original, though, and Lindsay Anderson's directing style is stagy. (Not rated) RATINGS: Films with ratings other than G may contain varying degrees of vulgar language, nudity, sex, and violence.