The movie "8 Mile" poses three questions: Can rap star Eminem act? Can he be a movie superstar? Is it a decent picture?

"Yes" to the third question, and "maybe" to the first two-though the deck is stacked in the rapper's favor.

In "8 Mile," Eminem, the foul-mouthed white rapper who took the pop music world by storm in 1999, plays aspiring Detroit rhymer/climber Jimmy "Rabbit" Smith. It's as good a movie showcase as any solo rock/pop superstar has had, with a classy production and a first-rate director (Curtis Hanson of "L. A. Confidential").

The Beatles' "A Hard Day's Night" remains out of reach, probably forever, but "8 Mile" definitely matches well against semi-bio rocker vehicles from Elvis Presley's "Loving You" to Prince's "Purple Rain."

Set in Detroit's 8 Mile, the dividing line between the city limits and the northern suburbs, "8 Mile" is an exciting, well-crafted movie, loaded with urban atmosphere. The central role is tailor-made for Eminem (a.k.a. Marshall Mathers): a troubled young white kid in a multi-racial neighborhood, trying to break through to fame in the cutthroat rap world. Eminem's gifts of verbal agility and acid ad-libs shine through in Jimmy's rap scenes and he has a simmering, moody presence that carries him in the dramatic episodes.

The movie is a rap rite-of-passage, and it follows Jimmy though initial failures-he chokes on the stage of The Shelter, the local rap arena-through scenes where he hangs with his buddies, dreams of stardom, copes with a troubled home-life (with mother Stephanie, played by Kim Basinger), gets burned by dirty girl Alex (Brittany Murphy) and finally brings it all home.

Eminem, who looks a bit like gritty British actor Tim Roth, holds the screen with a pop star's camera presence and instincts-though I wouldn't say, on the evidence here, that he's a natural movie actor the way Elvis was, or the way Cher, Ice Cube and David Bowie are, or were earlier pop music stars Frank Sinatra and Bing Crosby.

Here, though, he doesn't need to be; "8 Mile" is an unabashed "Rocky"/"Star is Born" story. Hanson keeps the picture firmly on track and moving smoothly toward the end we all know is coming: Jimmy's stage battle with mike-to-mike mic-to-mic combat, under the watchful emcee guidance of Jimmy's buddy, Future (Mekhi Phifer).

But that's a problem. We do know what's coming, in almost every scene. From Jimmy's tiffs with his beauteous trailer-trash mom and her slimy sponge, younger bedmate Greg (Michael Shannon), to his fling with slutty would-be model Alex to his wooing by local would-be mover-shaker Wink (Eugene Byrd), to his clashes with the local rap champs and his wild night with his guys, "8 Mile" doesn't give us anything we couldn't expect.

That's no real drawback if you see the movie as simply a pop musical/star vehicle, but it does put a semi-kibosh on its aspirations to urban drama. This is an only lightly disguised male Cinderella story custom-made for Eminem.

What's new and valuable is the well-observed milieu, and the way Hanson and cinematographer Rodrigo Prieto ("Amores Perros") bring it alive.

Hovering over the entire movie is the very promising dramatic idea of a white kid invading black inner-city turf, a fictional parallel to the ways Eminem achieved his fame in the hip-hop style with the help of black artist-producers like Dr. Dre-perhaps the partial inspiration for the character Future. That's a touchy, potentially explosive theme; it reminds us of Elvis, the white Mississippi kid who melded black rhythm and blues and white rockabilly into a potent crossover brew.

Potentially, it's a story about cultural assimilation, but the script turns it more into a male-bonding movie. Skewing the whole movie toward cliche is the way Jimmy's relationship with Future is sentimentalized. (With his hipster dreadlocks and paternalistic warmth, Phifer almost steals the movie.) It may have been a mistake though for buddy Future to also function as the Shelter's emcee, which makes the battles look semi-rigged. It might have been better to split the character up and make The Shelter's emcee a different guy, more hostile, another hurdle for Jimmy to clear.

Similarly, the relationship stuff with Jimmy's mother seems to exist mostly to exploit audience knowledge of Eminem's own mother-bashing lyrics and lawsuits. And the choice to hire writer Silver-whose first movie was "johns," a sympathetic portrayal of an urban gay scene-seems designed to answer complaints of homophobia in Eminem's lyrics, as does the scene where Jimmy trashes a gay-slamming rapper.

If "8 Mile" has one serious shortcoming, it's that it doesn't contain enough Eminem rapping. Prince's 1984 "Purple Rain" was also a pop-"Rocky," but that movie had a great original soundtrack by Prince as well. "8 Mile" is set in 1995 and its song track (though not the album to be released later) is jammed with period 1995 rap by other stars. Eminem's best number is under the closing credits and we only get a few of his performances before the final duel-when it would seem smarter to load the track with his songs, to build our appreciation of his skills as he battles and practices before his final showdown.

In the end, most of this doesn't matter. Movies with pop superstars in their first flush of fame carry a special shine and cachet when they're released, and "8 Mile" is a sometimes moving and thrilling example of this. Flaws and all, it really does show a star being born.