'Tremendous Interest' in a Mass Effect Movie, says BioWare
Because I found some.
Hmm... the thing is, they'd have to follow totally different characters since the whole idea of the game is that there is no 'canon,' but rather that you make the story move by your actions as you go along.
Also, there is so much in the way of backstories and explanations (usually in the Codex) that really help the world tick. It'd be hard to make the movie convincing to those who aren't familiar with the universe in a mere two hours.
I'd rather see a well-written miniseries.
Plus, can you imagine the way that an unrestricted Hollywood director would butcher the Krogans?
EDIT: Someone in the comments mentioned dealing with the story of Captain Anderson. That might indeed be cool to have a prequel movie, although I think that story has been explored in one of the books they wrote. Regardless, any Mass Effect movie should steer entirely clear of Shepard, since I know as a player and fan I would feel a little betrayed if "my" Shepard were overwritten.