I would definitely be Professor X....no contest. You can make anyone think or do absolutely anything you want. Free lapdances for life! It would suck to be paralyzed, but you could just use your telepathic powers to make everyone think that you were ambulatory.
Other than Xavier, I would think that Magneto's powers would come in handy the most.
Great call on Josh Holloway for Gambit! He was always my favorite character. Someone should e-mail Brett Ratner or Bryan Singer!