In Hollywood zoology, there are three common species of leading men: the pretty boys (Brad Pitt), the ugly mugs who can really act (Humphrey Bogart), and the regular guys (Tom Hanks). The rara avis of stars, though, is the actor in whom physical beauty and dramatic ability are fused into one iconic package. James Dean and Montgomery Clift were examples of this genus decades ago. In our time, we have Johnny Depp and Leonardo DiCaprio, both with Method hearts beating beneath their matinee idol exteriors. The two met up in the decidedly unglamorous comedy-drama What’s Eating Gilbert Grape and each has a movie just hitting video stores: DiCaprio plays junkie poet Jim Carroll in The Basketball Diaries and Depp is a seeming nutcase who fancies himself the world’s greatest lover in Don Juan Demarco.

As Grape‘s title character, a winsome and dutiful small-town stock boy, Depp gives a remarkably subtle performance. But it’s DiCaprio’s portrayal of retarded brother Arnie that earned an Oscar nomination (for Best Supporting Actor). DiCaprio relies on mimicking physical tics, sure, but he manages to reveal Arnie’s sweet but uncomprehending soul.

So it was with high hopes that most who had loved DiCaprio in Grape looked to The Basketball Diaries. No one could be better equipped to manifest the poetic spirit of Jim Carroll (upon whose novel/memoir the movie is based). Which makes this awful movie that much more of a shame. The film betrays Carroll’s book, and his life, in some bizarre ways: While the book takes place in the mid-’60s, the filmmakers set the movie in the present without updating the script — hence, the movie has ’90s racists referring to African-Americans as ”spades” and ’90s teens telling their mothers not to feed them any ”dime-store psychology.” And that’s among the least of the movie’s faults.

DiCaprio has a few affecting moments, which only serve as painful reminders of what might have been. At the end, when he performs a monologue describing the different social strata of the drug world, one thinks, ”Hey, that’s pretty compelling stuff. Too bad they haven’t shown any of it in the past 90 minutes.” In other spots, he falters. There’s the standard-issue withdrawal scene, all shivers and spittle accessorized with some Dawn of the Dead makeup. One can only assume that director Scott Kalvert is to blame here; after all, he botches everything else in the movie.

The older, savvier Depp has in recent years been adept at avoiding such pitfalls. It’s a measure of his self-knowledge — and his self-marketing acumen — that in Don Juan DeMarco he takes a role that seems a stretch but is actually a variation on the parts he played in Benny & Joon and Edward Scissorhands: the alienated oddball as great romantic. Here it’s the trappings that make the difference: Depp plays a modern-day Queens, N.Y., resident who insists he is Don Juan. With his Castilian accent and elaborate costume, he has an easy time convincing others of his imaginary identity. Rescued from a suicide attempt by shrink Jack Mickler (a very winning Marlon Brando), the great lover soon draws the psychotherapist into his lush fantasy world. Or is it a fantasy? Depp’s tales put the spark back into Mickler’s marriage and lead the therapist to question the worth of his own ”reality.”

A near-perfect confection that doesn’t wear out its welcome (the movie clocks in at a very tidy 92 minutes), Don Juan DeMarco glistens with such charm and goodwill that you barely notice that its central premise is a little sexist. And while Depp has little to do but look beautifully soulful, a breathtaking transformation scene at the movie’s end spotlights the actor’s chameleonic abilities.

With Depp’s career holding so steady, one may wonder what’s eating DiCaprio. Hopefully, The Basketball Diaries will turn out to be a mere setback. DiCaprio’s next turn is as poet Arthur Rimbaud in Total Eclipse, while Depp will be seen in the Jim Jarmusch western Dead Man, both appropriately offbeat choices for two serious-minded thespians who may yet become Hollywood icons in spite of themselves. What’s Eating Gilbert Grape: B+