With its narrative flow and debt to such drug-violence flicks as Scarface and King of New York, gangsta rap aspires to be sonic cinema. And it’s true that, despite its antisocial content, hiphop is much more showbiz-friendly than, say, folk-rock: LL Cool J, Queen Latifah, and Ices T and Cube all used their music as a path to mainstream acting careers. But acting, even just on cop shows and sitcoms, requires a vulnerability that’s irreconcilable with the grim visage of a tough-guy rapper like 50 Cent. Turning his multiplatinum Get Rich or Die Tryin’ into a movie is a logical way for 50 to expand his franchise, but that doesn’t guarantee he can enlarge his abilities along with it.

Though the performance of 50 Cent (born Curtis Jackson) is Get Rich’s weakest link, the movie constructed around it is nothing special. A fictionalization of the rapper’s official life story—which itself may be largely fiction—the movie opens with a botched robbery, flashes back at length to the childhood of its central character (here called Marcus), and then travels forward to a triumphant concert that announces Marcus’ transformation into world-beating rapper Young Caesar. In addition to altering 50’s real and stage names, the script modifies the lives and fates of the rapper’s parents, among other details. But it retains, of course, the reputation-making incident in which 50/Marcus is shot nine times at close range, a purported murder attempt in which, curiously, not a single bullet penetrates the victim’s torso or head.

The project’s wild card is the presence of Irish director Jim Sheridan, following In America with his first fully American movie. A product of some of Dublin’s scruffier streets, Sheridan has made such stirring but nuanced films as My Left Foot, The Boxer, and In the Name of the Father, in which troubled young men search for their fathers and/or sublimate their anger into constructive pursuits. Yet Sheridan’s skill as a director may be less important to the success of those movies than the fact that he wrote or co-wrote them. Here he’s stuck with a script by Sopranos veteran Terence Winter that’s a catalog of outsider-drama ready-mades. The filmmaker adds some antic touches (a slippery fight in a prison shower) and offhand commentary (John Kerry on TV denouncing CIA drug dealing), but he can’t prevent Get Rich from being merely a modern-day hybrid of a two antique genres: the gangster picture and the backstage melodrama.

As he battles generic long-haired Colombians to control the crack trade in a tough section of Queens, Marcus is pulled toward his sensitive side by his love for rediscovered childhood sweetheart Charlene (Joy Bryant), a dancer who has more class than the gyrating bimbos in the druglord den Marcus and his crew frequent. Inexplicably, classic good girl Charlene stays with Marcus even after she learns that he’s grown up to be a dealer and killer, waits for him while he’s imprisoned, bears his child, and nurses him after the nine-shot incident. Too neatly, Marcus’ breakthrough to rap renown is framed by the discoveries of his father and of the identity of his mother’s murderer. The cornball capper, rendered goofily psychedelic by Sheridan, is a frantic montage of Marcus’ near-death experience and spiritual rebirth, intercut with his original delivery and fireworks bursting in air, because he’s a Yankee Doodle–drug–dealer, dark-soul-of-racist-America baby born on the Fourth of July. (Technically, 50’s birthday is July 6.)

Sheridan goes easy on 50’s nasty-nursery-rhyme tracks, relying heavily on only two—“I’ll Whip Ya Head Boy” and “Window Shopper”—while using a score co-written by Dublin pals Gavin Friday and Maurice Seezer. Get Rich is much less a showcase for its star’s music than their various big-screen vehicles were for the likes of Elvis Presley and the Beatles—but then, both the songs and the personae of such performers were considerably friskier. 50 Cent is a stolid presence, barely more expressive when his jaw’s not wired shut—something that’s only emphasized by the dynamism of such supporting actors as Terrence Howard (as Marcus’ volatile jailhouse friend Bama). Sheridan, who proved himself as a director of kids with In America, does get a believable performance from Marc John Jefferies as the young Marcus. The bright-eyed kid’s transformation into the dead-gazed Young Caesar suggests an alternate title for this anti-bildungsroman: Get Shot, Get Rich, Get Boring.

Whereas gangsta rap’s essential gambit is to make cartoonish fictions play as “4 real,” mainstream American action movies flip the formula: They provide plenty of genuine-looking violence, softening it with ironic humor. One of the originators of this recipe is Shane Black, who briefly became a movie-biz legend by writing (and selling) the script for 1987’s Lethal Weapon when he was just 23. Black’s reputation faded as subsequent projects flopped, and he vanished altogether after 1996’s The Long Kiss Goodnight, as Quentin Tarantino became Hollywood’s new master of the sardonic bloodbath.

So it’s to be expected that Black’s rebirth as a writer, and debut as a director, is as heavily footnoted a genre-mocking exercise as Pulp Fiction. Kiss Kiss, Bang Bang takes its title from a collection of writings by film critic Pauline Kael, its chapter headings from Raymond Chandler, and the style of its opening credits from ’50s and ’60s animator/designer Saul Bass. The result is bustlingly self-amused, and the movie’s pleasure in its own cheekiness makes it fun to watch, if not to ponder.

After a prologue set in innocent Indiana, Kiss Kiss, Bang Bang introduces its central character, Harry Lockhart (Robert Downey Jr.). Or rather, Harry introduces himself—as not only the film’s narrator but also its demiurge. Like any respectable Mel Gibson character, Harry gets brutalized repeatedly. Yet his misfortunes can never be taken seriously, because he’s in charge of the story: He can interrupt the action, rewind the narrative, cue the flashbacks, and interject digs at Drew Barrymore’s sex life, so you have to wonder why he doesn’t just hit Pause every time he’s about to get thrashed.

As Harry explains, he’s a small-time thief who, while running from New York cops, blundered into an audition. Improvising on his actual situation, Harry impressed the scout, who had him sent West for a possible movie role. In Los Angeles, Harry is apprenticed to homosexual gumshoe Perry van Shrike (Val Kilmer), aka Gay Perry, who’s supposed to show Harry how real PIs work. But Perry’s tutorial intersects an actual murder case, and soon Harry is courting danger in earnest—or as earnestly as a movie this contrived can get. The homicide also entangles actor Harry Dexter (Corbin Bernsen), who used to play hard-boiled detective Johnny Gossamer on TV, and aspiring actress Harmony Faith Lane (Michelle Monaghan), who just happens to be Harry’s classmate and teenage crush from back home in Indiana. Although Harmony eventually claims that Tinseltown has brutalized her, she doesn’t look it. (In fact, the 29-year-old Monaghan appears, oh, about 11 years younger than the 40-year-old Downey.)

Aside from Harry’s glimpse at the naked crotch of a female corpse, the movie’s sexual content is entirely PG, and strictly for giggles. (Gay Perry is gay mostly for the sake of his punning name.) What really earns the flick an R is its gross-out material, including lots of play with a severed finger and that cadaver, which just won’t go away.

For all its absurd complications, the plot is ultimately unsurprising and not all that interesting. But the film’s playful energy is contagious, and some of the nastiest bits are capped with amusingly self-deflating gags. A showcase for Downey as much as Black, Kiss Kiss, Bang Bang does considerably less for Kilmer and Monaghan. But the star’s likability takes a hit during the final credits, which feature a number by would-be modern-cabaret singer Robert Downey Jr. For this attempted comeback by a writer and two actors who peaked too soon, couldn’t they have spread the karmic wealth by using something from Axl Rose?CP