I usually manage to - at least at some point - play the game again, and usually do it as an evil character then... But I tend to stall on those playthroughs and not finish them. It just isn't as interesting playing it a second time, usually. And playing an evil character really is so much easier! You end up skipping half the dialogue and every sidequest ends with killing everything possible. At least when you play a good character you have some thinking to do about who you're supposed to be killing.