I'd go:

Michael Keaton
Eddie Redmayne
Benedict Cumberbatch
Steve Carell
David Oyelowo

In that order. Keaton and Redmayne are locks, Cumberbatch is close to a lock. Carell has more buzz than Oyelowo because he's a bigger name and his cast has more star power in general. Oyelowo just needs to stay in front of people like Bradley Cooper and Jake Gyllenhaal. I think Jake's movie is too dark to sneak in. I'd imagine Cooper's film will play well, just an issue of if the Academy thinks it's an "Oscar film."

Still, Oyelowo's issues is, as it has been, name recognition. In order to win Oscars, people have to see your film. And the Academy almost always prefers films with star power. Critics can help steer a movie into the Academy's line of vision, which is Selma's best shot.