In a wide-open Best Picture race, this sprawling, moving film is a leading contender. Its main competition is considered, a little more than a week before the awards broadcast, to be “The Departed” and “Little Miss Sunshine.”

A wakeup call for all of us who have purchased diamonds, “Blood Diamond” reveals a dark side to the gem trade in Africa. Set during the civil war in Sierra Leone, the film shows how strongmen used forced labor to find diamonds in the country – where diamond exports were illegal – and then bribed officials across the border in Liberia, who mixed the “blood diamonds” in with the broader supply of diamond exports.

Leonardo DiCaprio stars as a diamond smuggler who has his consciousness raised over the course of the film, as he struggles with his own motives in helping a former slave (Djimon Hounsou) recover a hidden diamond. Jennifer Connelly stars as a journalist working with DiCaprio to expose the illegal smuggling operation.

Beautifully shot by Eduardo Serra, “Blood Diamond” is visually arresting and features fine performances from its principal actors. But the film grows tedious during the long hunt to discover the hidden gem. Every time the film slows down to focus on character interaction, an explosion or gunfire intrudes, reigniting the chase that gives the film an artificial sense of momentum, when a little more thoughtful reflection would have better served the film.

Brooding, bloody and violent, “The Departed” puts director Martin Scorcese back on the turf on which he made his name with “Mean Streets,” “Taxi Driver,” “Raging Bull” and, later, “Goodfellas.”

The public responded approvingly, making “The Departed” by far the top-grossing film among this year’s Best Picture nominees. The story of two Boston police officers with competing agendas, each trying to root out the other, was powered by Leonardo DiCaprio’s most mature performance to date (ironically, he was nominated for lesser, but still noteworthy work, in “Blood Diamond”), matched by Matt Damon, in one of his best performances. But the film’s strength comes as much from its supporting cast – Jack Nicholson, Martin Sheen, Alec Baldwin, and the Oscar-nominated Mark Wahlberg.

A remake of the Hong Kong thriller, “Infernal Affairs,” “The Departed” runs 50 minutes longer than the original and features more excess all around – more profanity, more bloodletting and more over-the-top acting. But the public soaked up this cold, brutal film. At least one sequel already is in the works.

This highly hyped movie is a respite from most of the other major Oscar contenders in several ways – joyful and exuberant during its first half, and extending across several years, this musical received a leading eight Oscar nominations. But in what came as the year’s biggest Oscar-related shock, “Dreamgirls” was not nominated for Best Picture or Best Director. Three of its nominations come in the Best Song category, while its most noteworthy nods are for Eddie Murphy’s fantastic, energetic performance as soul singer James “Thunder” Early and former “American Idol” also-ran Jennifer Hudson, for her breakout role as Effie White.

“Deamgirls” spans several years as it tracks the career trajectory of an all-girl singing trio and the performer (Early) who helped give them their first break. As the public’s taste in music changes, and as the era of music on the radio gives way to an era of TV performances, the Dreamgirls redefine themselves, at the behest of their craven manager (Jamie Foxx). Their story is one of so many soul performers, who fought discrimination only to see their work widely embraced after the same songs were popularized by white performers.