That rather depends on what kind of evil they're going for. If it's the rather silly 'be a jerk to people for no adequately explained reason', then I probably won't go that route no matter how many rewards the game would inexplicably give me for that approach (lookin' at you, Fable 3).
If it were more of a ruthless, self-serving, mad-with-power kind of evil, I might be tempted to go that route on a second or third playthrough.
