The power of Eminem’s music lies in its unsettling ability to channel the darkest depths of his harrowingly scarred psyche. He is abnormally honest, a shocking deviation from the sugar-coated popular musical tradition of masking true emotions with clever metaphors. He says what he feels, even if these emotions are blatantly homophobic, ignorantly misogynistic, or excessively violent. Even more than his rap predecessors, he gives the craft a kind of stream-of-consciousness, a poetic jolt of unburdened therapeutic expression that elevates his work to the level of lyrical storytelling.

It is no surprise, then, that his feature film debut “8 Mile” cannot even hope to match the reverberating surge his rhymes emanate. In spite of Eminem’s best efforts and director Curtis Hanson’s (“L.A. Confidential,” “Wonder Boys”) offbeat style, the movie is very, very Hollywood. Producer Brian Grazer is a pro at telling interesting tales within the confines of commercial film industry requirements (see “A Beautiful Mind” if you need evidence). Here he turns the gritty slums of Detroit into a setting for the against-the-odds, triumph-over-adversity chutzpah that marketers crave. It is done all the time in this avaricious industry, but with Eminem, one can’t help but hope for a little more harsh moral ambiguity than the film explores. In fact, it follows the same overcome-your-fears triumph that Grazer employed in last summer’s superior surfer girl flick “Blue Crush.”

But even amidst this mainstream “Rocky” formula, Hanson offers some fresh drama. He successfully conveys his “fictional” aspiring musician Bunny Rabbit’s need to break free from the very world that inspires his most aching musical expressions of pain and hate. Hanson also mines intrigue from the fact that the audience is viewing the roots of Eminem’s pop-culture iconic status. It is an episode of “Behind the Music” fictionalized and stylized, a tale of an artist told by an artist.

Hanson also makes the tension between Rabbit’s fear of expressing himself and his drive to succeed by that very self-expression vivid and touching. In the film’s opening, Rabbit chokes in a rap battle with the area champion. This early failure is not only humiliating, but it also seems to reinforce the shell that keeps him from realizing his true potential. This fear, this inability to take risks and face the crowd, haunts Rabbit for the rest of the film; it pushes him forward and holds him back all at once.

The usual collection of supporting characters provides either the encouragement or oppression that paves this difficult road to success. Kim Basinger plays the cliched “un-motherly” white trash mother, and while she is a bit shrill, her scenes establish the home life Rabbit desperately wants to leave behind. Brittany Murphy is Alex, the story’s requisite supportive love interest. Murphy plays the character to enjoyable sex kitten extremes, but the movie’s emphasis on her unalterable belief in Rabbit is a little over-the-top. After the pair engages in a raw sexual encounter in between the massive pumps and presses of a factory, she breathlessly tells him that she “knows he’s going to make it.” So is an orgasm supposed to be the erotic equivalent of an inspiring pep talk? Finally, Mekhi Phifer fits the niche of the supportive best friend who pushes Rabbit to succeed where he never could.

All these performances serve their purpose without being extraordinary. They also underscore that this movie really is the Eminem show. While Eminem the actor can’t completely capture the passionate rage that Eminem the musician possesses in spades, he mesmerizes at times with his explosive depiction of pent-up aggression and ambition, proof that the real Slim Shady has uncovered some thespian muster. He may only be recreating his past, but it is fiery, vibrant work from an amateur. The actor, as well as the film, comes to especially powerful life in the rap scenes. It is here that Eminem can adapt his real unique talents to the emotional context of the film. He makes up a rap to “Sweet Home Alabama,” spontaneously decides to battle an abusive co-worker at the factory with biting lyrical criticism, and, in the final showdown, faces his rapper nemesis with a rushing river of verbal power, a tirade that both admits his faults and breaks from their self-destructive results. It is here that the movie finds its rhythm. It is here that we can breathlessly watch the masterful genius of a true artist emerge.