The opening credits feature Woody Allen's trademark white letters on a black background, with a jaunty version of ''It Had to Be You'' on the soundtrack. The score is rich with Gershwin, the camera infatuated with Manhattan, the dialogue obsessed with love, sex and death. Altogether, Rob Reiner's ''When Harry Met Sally . . .'' is the most blatant bow from one director to another since Mr. Allen imitated Ingmar Bergman in ''Interiors.''

On and off for 11 years, Harry (Billy Crystal) and Sally (Meg Ryan) ostensibly debate whether men and women can be nonsexual friends. But that issue instantly evaporates and the question becomes: When will they realize they were made for each other? What Harry and Sally do in the meantime - the true focus of this often funny but amazingly hollow film - is saunter through the romanticized lives of intelligent, successful, neurotic New Yorkers.

Harry and Sally's version of the city offers constant jolts of recognition, as it dwells on carefully specified landmarks and echoes ''Annie Hall'' and ''Manhattan.'' At the Temple of Dendur in the Metropolitan Museum of Art, they discuss dating. In autumn, they stroll by gloriously bright trees in Central Park (Sally wears an Annie Hall hat) and describe their recurring sex dreams. They walk by the glittering Christmas display at Rockefeller Center and the decorated windows at Saks Fifth Avenue. And when Harry and Sally join their two best friends at a SoHo restaurant, half of the people at that table write for New York magazine.

Mr. Allen can get away with such a rarefied vision because, as he put it in ''Manhattan'': ''He adored New York City. He idolized it all out of proportion.'' Gently mocking his own romanticism, Mr. Allen gives his films depth and a believable, astringent undertone. But Mr. Reiner has a simple faith in fated love, which makes his film cute and sentimental rather than romantic and charming. ''When Harry Met Sally . . .'' is like the sitcom version of a Woody Allen film, full of amusing lines and scenes, all infused with an uncomfortable sense of deja vu.

When Harry and Sally first meet, in 1977, they are University of Chicago graduates driving to New York together. Harry seems carefree, but is pessimistic enough to read the last page of a book first; in case he dies, he says, at least he'll know how it ends. And know-it-all Sally insists that Ingrid Bergman really wanted to leave Humphrey Bogart. ''I don't want to spend the rest of my life in Casablanca with a guy who owns a bar,'' she argues, in a line that nails precisely who she is at that moment. Ten years later, after Harry's wife has left him and Sally has broken up with her boyfriend, they become best friends.

Mr. Crystal and Ms. Ryan are appealing and sometimes even unpredictable. Mr. Crystal has the wittiest lines and snappiest delivery, but he also shows Harry to be remarkably gentle, a sensitive mensch. Ms. Ryan has the more subdued role, and the two most volatile scenes. She hilariously and loudly fakes an orgasm in a crowded deli, and goes on a truly mournful crying jag when she learns that her former boyfriend is getting married.

Yet in Mr. Reiner's conception, and in Nora Ephron's screenplay, Harry and Sally are defined by their witty, epigrammatic dialogue and so never become more than types. Sally is a journalist who occasionally sits at her home computer and stares into space; Harry's job as a political consultant is even more shadowy. As their best friends, Carrie Fisher and Bruno Kirby are at least meant to be types, and both bring some flair to their roles. She is a marriage-starved woman who totes around an index file of men's names and he is a woman-shy man. Miraculously, these two are also perfect for each other And Mr. Reiner's belief in miracles goes far beyond their comic pairing. Throughout the film, he inserts mock-documentary scenes in which long-married couples face the camera and briefly tell their stories of love at first sight, or of love lost and later found. It is much too blunt a way of pointing to Harry and Sally's future.

Oddly, Mr. Reiner's best, most inventive films - ''The Sure Thing'' and ''This Is Spinal Tap'' - have precisely the sly edge and sardonic tone that ''Harry Met Sally'' needs. His most recent films, ''Stand by Me'' and ''The Princess Bride,'' are softer and more nostalgic. And like a sitcom with too much canned laughter, ''When Harry Met Sally . . .,'' which opens today at the Beekman and other theaters, is a perfectly pleasant Woody Allen wannabe, full of canned romance. DOWN ALLEN'S ALLEY - WHEN HARRY MET SALLY . . . directed by Rob Reiner; screenplay by Nora Ephron; director of photography, Barry Sonnenfeld; film editor, Robert Leighton; music by various composers; production designer, Jane Musky; produced by Mr. Reiner and Andrew Scheinman; released by Castlerock Entertainment. At the Beekman, Second Avenue and 65th Street. Running time: 95 minutes. This film is rated R. Harry Burns...Billy Crystal Sally Albright...Meg Ryan Marie...Carrie Fisher Jess...Bruno Kirby Joe...Steven Ford Alice...Lisa Jane Persky Amanda...Michelle Nicastro

photo of Meg Ryan and Billy Crystal