Back when Peter Jackson was attached to the Halo movie project the plan was for Neill Blomkamp to direct it. The movie famously fell through, and Blomkamp went on to make District 9 - a movie that dealt with the division in South Africa by adding an alien component. Speaking to IGN as his latest effort Elysium is about to go up, Blomkamp expressed interest in returning to Halo.
"I still really love the world and the universe and the mythology of Halo. If I was given control, I would really like to do that film. But that's the problem. When something pre-exists, there's this idea of my own interpretation versus 150 other people involved with the film's interpretation of the same intellectual property. Then the entire filmgoing audience has their interpretation. You can really live up to or fail in their eyes. That part isn't appealing to me, but the original pieces are appealing."
Remains to be seen if a Halo movie ever comes to fruition.