How about the reverse: "can you still be a bad guy if you always play a good character?"
I think the result is exactly the same: the character you play in a video game most likely does not reflect the kind of person you are in real life. Even though I saved the Capital Wasteland with maximum positive Karma in a video game, I am still able to, for example, shoplift candy bars and vandalize public property and possibly enjoy doing so. Sometimes even go too far with a practical joke leading to slight bodily damage and still find it hilarious. But as a whole, I'd say in real life I'm hovering slightly between Good Karma and Very Good Karma.
However, I've noticed something about playing the good guy for too long. Does anyone else feel aversion to playing an evil character in a video game? It seems I can't bear to get the bad karma achievements in Fallout 3; I pick the most standard evil responses and kill as many good and/or neutral NPCs as possible, but after a while I feel as if I'm playing the game incorrectly, same the game, and quit. It's like a Clockwork Orange effect where I become repulsed by being the bad guy.
The same goes for other games like Grand Theft Auto 4 (committing as few crimes as possible) and Red Dead Redemption (I break for pretty much every random event in the wilderness). Years of being the good guy has made me averse to being the bad guy, so much so that I can't stand being a bad guy at times.
