In games like Fallout, I usually try to play as the good guy, though there's some wiggle room in that depending on some decisions that can be made. Even if it is all fictional, I never like playing the asshole, it's just so out of character for me that it doesn't bring me a lot of enjoyment. That is sorta sidestepped in other games like Grand Theft Auto where you play as criminals and there's no real negative repercussions to being one and is a big part of the game, but generally like Skyrim, Fallout, Mass Effect, I'm trying to play as the good guys.