Christopher Wallace created a character who was born for the big screen - or the B.I.G. screen, as he would doubtless have had it renamed for the occasion. Biggie was barely inside the recording studio before he was exaggerating the poverty from which he came ("I remember when I used to eat sardines for dinner," as he had it on Juicy - a claim hotly denied by his proud schoolteacher mother) and the riches into which he'd come. The tragedy - unforeseen, no matter what those album titles said - is that he isn't up there playing himself.

The title role in this biopic goes instead to two debuting thesps. First, his son, Christopher Wallace, Jr., plays the young version of his father, the kid whose dreams of being a rapper are mocked by the girls because he's too "fat, black and ugly", not to mention speccy. The role of the adult - still fat, black and ugly, but now just two-eyed - goes to Jamal Woolard, aka mixtape rapper Gravy, a decision which must have caused an outbreak of potty-mouth from Guerrilla Black's home to Shyne's prison cell.

Woolard does a creditable job (better than Fiddy playing himself in Get Rich or Die Tryin', for what that's worth), coping brilliantly with the many music scenes and acquitting himself comfortably with the emotional range required. This is not all it might have been: the script, by Vibe scribe and Biggie biographer Cheo Coker and Get on the Bus screenwriter Reggie Bythewood, lacks spark, weighed down in its determination to join the dots from one significant event to the next. It's like watching a meticulously detailed Wikipedia page acted out in front of you; bullet points given dialogue. The framing device - the shot and dying Biggie providing a voiceover on his own life - is also over-familiar from gangster movies, from the major (Carlito's Way) to the minor (DMX vehicle Never Die Alone).

There's also the inevitable problem of the unsolved murder, a mystery that's left unavoidably open, since the prime suspects are still alive and, potentially, litigating. The relationship with Tupac (Anthony Mackie) is fine, then it evaporates in a puff of gunsmoke at Quad Studios. Again, possibly for legal reasons, the producers are unable to truly get under the skin of Tupac's madness, a lack of dramatisation which, oddly, makes the finale that bit more depressingly senseless. Puffy, who co-produced, is cast as selfless, hyperactive mentor, a depiction that won't thrill his detractors. Notorious is, though, terrific on Biggie's women. Faith Evans (Antonique Smith) is a level-headed church girl drawn into a world she wants to avoid. Lil' Kim, a loose cannon alternately raging at Biggie or putty in his outsize hands, is given a sparky, sensitive portrayal by Naturi Naughton who, in art as in life, is obliged to display herself for the boys. Angela Bassett plays Biggie's mother, Voletta, a rock of good sense trying to instil responsibility in the young megastar.

She takes over the narration after his death, giving her the film's one genuinely moist-eyed moment, her reaction to the extraordinary Brooklyn street party that erupted following Biggie's funeral. It intercuts between her shock and swelling pride and actual footage of the event, familiar to anyone who's seen the Nick Broomfield documentary, Biggie & Tupac. It's a fusion of fact and fiction Notorious' subject would've appreciated, and a reminder that no screen, however big, could fully capture everything Biggie.