As good as Muller's performed Messi has been better. Bayern perform better as a team but Messi has played better, how he destroyed AC Milan at the Nou Camp almost single handed.A Bayern player should absolutely, 100% be given the Ballon D'Or. I don't think an argument can even be made otherwise.
Muller is my pick. Lahm, Ribery, Robben would all be contenders. Muller is just something more special this year.
It's hard to look past him.