Well, Radar's post actually got me to thinking (amazing on a number of levels, eh?
). Its true that just about everyone believes themselves to be a "good" person. I think the exception would be sociopaths, and they would consider the question irrelevent.
People with the best of intentions can do some pretty awful things through ignorance or denial or fear, and you don't have to be Hitler, either, to do them. When I look back on my life, I see some actions that were pretty misguided, although, at the time, I thought I was doing the right thing or at least was justified in my deeds.
If we label ourselves "good" or "bad" we are engaging in black and white thinking and indulging in a line of thought that can only contribute to an "us versus them" mentality. I'm "good" and they're "bad," so off to the ovens with THEM!
Human beings are complex critters and on a good day can be saints and on a bad day, the same person is one everyone would run from. Then you have to take the prevailing culture into consideration. Today, we would consider anyone who burned people at the stake "bad." 500 years ago, such acts were considered just and "good."
"Good" and "bad" are just not useful labels, all in all.