Dir: Michael Mann. US 2001. 159mins.

The challenge of how to present dramatically the life of Muhammad Ali, arguably the most recognisable and flamboyant celebrity of the 20th century, is only partially met in Michael Mann's Ali. An ambitious but flawed film, it narrowly focuses on one decade in the prizefighter's existence - 1964 to 1974 - while gliding over his private life and neglecting other aspects of his turbulent, yet always fascinating, career. Physically transformed to match Ali's figure at his prime, Will Smith - who gained more than 35 pounds for the role - gives a commanding performance as a man who became extremely controversial due to his conversion to Islam and draft resistance during Vietnam, before winning the championship in the much publicised Rumble In The Jungle fight in Zaire. Although Columbia's Christmas release in the US will be heartedly embraced by black patrons and sports fans, Ali is also likely to appeal to wider demographics, due to its big event nature, Ali's celebrity status and Smith's star power among both black and white moviegoers. However, with a production budget estimated at more than $100 million, and an extremely expensive marketing campaign, Ali the film may not be the box-office greatest Sony was hoping for -unless it garners major Oscar nominations and awards.

It's easier to respect than to like Ali, a film that is more noteworthy for its ambition and intent than execution and overall result. In various interviews, director Mann has said that Ali is "categorically not a biopic", and that what he and star Smith were trying to do was "something more extreme". Judging by what is onscreen, that "something more extreme" registers as notes or observations on the life of Ali as a great man, rather than a fully realised dramatisation of a unique figure who began as a product of his surroundings but quickly turned, as a result of talent, charisma and sheer chutzpah, into a master of his fate, conquering in the process both the sports and media worlds.

For weeks there have been rumours of how the cut that Mann presented to Columbia was not only longer but also more substantial and dramatically involving. In a season in which most Hollywood films run for more than two hours (and Harry Potter, which is no more than a children's fantasy, boasts a 152-minute running time that's only six minutes shorter), Mann should have had the right to show a three-hour-picture, given the rich, dense and heroic life of his subject. Fortunately, fans of The Greatest - and of director Mann - will have a chance to see additional footage in the upcoming DVD.

But the problem is not just length but also what the filmmakers have chosen to show - and not to show - about a man whose power and fame extended way beyond the boxing ring. The strategy of the screenplay, co-written by Rivele, Wilkinson, Roth and Mann, is to locate quintessential moments in Ali's life that are illuminating and emblematic of his whole existence. Indeed, Ali is a film of many great moments (and scenes), although, ultimately, it lacks the narrative coherence and political resonance of The Insider, Mann's previous, far superior, effort, which won critical kudos but was a commercial failure.

In the early episodes, after an overlong montage of images accompanied by Sam Cooke's music, Cassius Clay (Ali's name before he converted) is depicted as a young and aggressive fighter who wrests the heavyweight championship from Sonny Liston at the age of 22 in 1964.

Arguably the most intriguing chapters are those which deal with Ali's problematic approach to religion and politics, covering the same territory and controversial figures - albeit from a different angle - as films like Spike Lee's intriguing Malcolm X and the simplistic Panther, directed by Mario Van Peebles (he also plays Malcolm X in Ali). America is shocked when the newly named Ali declares his conversion to Islam and, later, finds himself torn between black separatist leaders Elijah Muhammad and Malcolm X, when the latter is suspended from the Nation of Islam. Interesting segments show the wrathful reaction of Ali's father (Esposito) to his son's religious change of heart, as well as the vicious murder of Martin Luther King Jr (Burton) and its impact on the still politically evolving Ali. According to Mann's fair, balanced view, Ali emerges as a man who, despite a rebellious streak, was not too militant in his attitudes toward dominant white America (whose support and love he sought) or other ethnic minorities, such as Jews.

Ali's refusal to enlist during the height of the Vietnam war - and the stripping of his title due to his draft evasion - offer the film's most dramatically involving chapters, framed as the battle of one conscientious individual against the US Army. It's around this time that Ali became famous for his one-liners (such as "ain't no Vietcong ever called me nigger"), and began to assume heroic stature due to his stamina during a tough three-year court battle that resulted in a unanimous acquittal by the Supreme Court.

For sheer entertainment, the feature offers half-a-dozen priceless scenes that chronicle Ali's relationship with Howard Cosell, a TV sports announcer. Playing the story's flashiest character, the unrecognisable Jon Voight does a pitch-perfect impersonation of the sportscaster, whose career was greatly assisted by Ali granting him exclusive interviews, replete with bombastic statements and personal revelations.

The film's most dissatisfying omissions concern Ali's private and family life. Since Ali is still alive, Mann and his team have possibly been too restrained or apprehensive about dealing with Ali's relationship to women; as is known, Ali has been married four times and is the father of nine children. The feature acknowledges Ali's first marriage to Sonji (played by Smith's wife, Jada Pinkett-Smith) and his inexperience in the bedroom in several soft and romantic moments. However, Ali barely throws a glancing look at its hero's courtship of other women, black and white, and his next couple of marriages. Rarely showing any of his kids, Ali the movie neglects its protagonist's parental roles and values.

An extremely complex and complicated man, Ali cultivated various, often contradictory persona, for different audiences: champion, troublemaker, loudmouth braggart, original rapper, shrewd diplomat, womaniser, family man - and above all else, a man whose gusto for life and the limelight was boundless. But Ali the movie vividly captures only some of these facets. At its weakest moments, the picture comes across as the triumphant story of a man who, after winning the heavyweight championship, loses the title and begins a long arduous struggle to regain his crown, discovering in the process that time has taken its toll and robbed him of his prowess as he's about to contest George Foreman, his younger, stronger foe.

The boxing scenes are impressively shot by Emmanuel Lubezki; considering there have been many prizefighting features, from Rocky to Scorsese's Raging Bull, the film shows in minute detail the moves and countermoves as planned and executed by the rivals and the tense pauses between rounds. But once again, what the film lacks is a distinctive perspective on Ali's talents as a fighter, what made him a champion and how different his boxing methods were from those of his opponents. Hence, one of the story's most obscure figures is Angelo Dundee (Silver), Ali's trainer from his youth - but of the entire support