The rap star 50 Cent has led a storied life, a rags-to-riches yarn that has become the stuff of pop legend: Born Curtis Jackson and reared in Queens, New York, Jackson never knew his father and lost his mother, a drug dealer, when he was only 8. Later he became a dealer himself, going in and out of jail for dealing crack until deciding, in the mid-'90s, to pursue a career as a rapper. Columbia Records had signed him and his first record was about to hit the streets in 2000 when Jackson (Mr. Cent?) was gunned down; shot nine times, he survived and went on to make headlines, not only for his infectious beats and lyrics, but for his frequent brushes with the law.

Good stuff and ripe for the cinematic telling, but "Get Rich or Die Tryin'," 50 Cent's fictionalized life story in which the rapper plays himself, is shockingly inert. While rap fans have no doubt eagerly awaited the big screen debut of their hero -- whose hulking, tattooed physique belies the soft-spoken boy-man beneath -- film fans have been curious about the film's director, Jim Sheridan ("My Left Foot," "In America"), whose commitment to classical, deeply humanist filmmaking would seem to be at odds with the grislier values of gangsta rap. Whether it's because Sheridan indeed wasn't a good match with the material, or because 50 Cent is such a poor actor, or because a life of crime -- which at the end of the day is a life of base stupidity and greed -- is really quite boring, "Get Rich or Die Tryin' " ain't rich, it's just tryin'.

The movie opens with a very cool credits sequence, set to the pounding strains of "I'll Whip Ya Head Boy" (the soundtrack features all new songs) while an image caught in a rearview mirror shakes with each vibration of the bass line. But the street-level energy of those shots quickly gives way to an episodic -- and, one suspects, revisionist -- retelling of 50 Cent's life, in which the rapper plays a character named Marcus, an enterprising hustler who only reluctantly resorts to violence. Familiar figures show up in fictionalized versions, including 50 Cent's real-life rival Ja Rule, here embodied by a "wanksta" named Dangerous.

Unlike "8 Mile," a similarly conceived film in which Eminem -- 50 Cent's real-life patron and producer -- portrayed his years coming up in Detroit, "Get Rich or Die Tryin' " barely features any rap. (Viewers who want to see 50 Cent perform must slog through two hours of his increasingly tiresome thug-life story, until the movie's closing credits, and forget about hits like "In Da Club.") Instead, Sheridan and screenwriter Terence Winter have inexplicably focused on the tiresome machinations of the drug trade, wasting a lot of time on a feud with some Colombians and 50 Cent's -- er, Marcus's -- relationship with a self-important crime boss, played by the great Bill Duke, affecting his best Brandoesque whisper.

Whether he's at a party or in prison, Marcus dutifully writes his raps, at one point ignoring a throw-down in his own house to scratch out lyrics in a marble-covered schoolbook. Later, he gets together with a childhood girlfriend (the lovely Joy Bryant), who not only brings out his teddy-bear sweetness but, after she gives birth to his son, his ambition. Marcus always manages to stay above the most violent, murderous parts of the fray, but 50 Cent himself remains oddly distant and detached as a performer. The audience is supposed to take it on faith that, with his admittedly disarming smile and shy demeanor, he isn't simply a hood who got lucky, but a warrior with the soul of a poet.

Even if that's true, it doesn't necessarily make for exciting cinema. In fact, the movie only perks up about an hour and a half in, when Terrence Howard -- who played a similar, much more engaging character in last summer's "Hustle & Flow" -- arrives as Marcus's prison-buddy-turned-manager. (The scene in which they meet looks like a prison fight as imagined by D.H. Lawrence by way of Larry Kramer.) This year, Howard has joined Peter Sarsgaard as one of the best reasons to go to the movies; as he did in "Hustle" and "Crash," he delivers an indelible performance, here as an aspirant to the American Dream who has all the verve, humor and congenital charisma that the film's star so sorely lacks.

Throughout "Get Rich or Die Tryin' " Marcus and his boys engage in the ritualized aggression celebrated in gangsta rap, always couched in the rhetoric of respect, potency and dominance. (The young Marcus, played by Marc John Jefferies, plasters his bedroom with Public Enemy and KRS-One posters, wistful reminders that rap was once a vehicle for provocative agitprop rather than macho posturing.) But the pumped-up poetry has always seemed to be more about self-mythologizing than authentic street cred, and "Get Rich or Die Tryin'," sadly, is no different. As Howard's character says in the film's first genuinely observant moment: "I see you have a little Napoleon thing goin' on there." Word.

Get Rich or Die Tryin' (134 minutes, at area theaters) is rated R for strong violence, pervasive profanity, drug content, sexuality and nudity.

Rapper 50 Cent makes his film debut in "Get Rich or Die Tryin'," based on his life as a drug dealer. Rapper 50 Cent, top, with Joy Bryant, makes his movie debut in a script based on his rags-to-riches life story. His music, right, however, is barely featured. Terrence Howard, below left, with 50 Cent, is the film's one true spark.