And roleplaying a vampire makes you... what?
I don't know about everyone else, but for me there's absolutely no connection between the real me and the character I roleplay. If I tried to base the character's actions on my own, I'd never play any game except for Tetris. I mean, let's be real, you HAVE to kill to complete the MQ - and we can safely assume the vast majority of gamers would run away screaming if they had to face a dragon IRL. The whole point of playing a game is to do things you'd never do in reality, be it because you can't or don't want to.
It's especially funny to me that you're asking about thiefs. My first choice in any game is a stealthy, roguish character. I strike from the shadows, go where I'm not supposed to be, get my way with no respect for the law. And yes, I steal everything that's not nailed down. Does that mean I'm like this in real life? No, not by a long shot. I haven't stolen a thing in my whole life. In fact, I'm studying to be a lawyer (though I'm not sure if it makes any point, depends what you think about lawyers

)
Maybe it's a part of me that's locked away, something I fantasize about. It's unlikely, but possible. Even if it is so, people should be judged on what they actually do, not on their fantasies or what they're capable of. We're all capable of killing, e.g. in self-defense. Does that make us all murderers?
I have various character in Skyrim. A calm and collected scholar. A cynical, emotionally crippled assassin. An honorable warrior. A goody-two-shoes alchemist who always carries a big stick, just in case.
If your theory was true, I would have a severe case of multiple personality disorder.
Not to mention that I'm a vegetarian, but tossing fireballs at the blood-thirsty Skyrim bears brings me unspeakable satisfaction. Heck, maybe I do have some unresolved issues...
