I was going to say that crazy people can do evil with no gain, but then I realized that it would suit their crazy logic, ie do them good. Very interesting point!
My personal view (before entering this thread) is that good cannot exist without evil, one implies the other, as suggested. I'm sure I could be considered evil next to Gandhi, but still more people could be considered more evil than me - this makes me good. In a perfect world, where I was the least good person alive, would not many consider me evil? Then again, they'd also be evil for thinking less of me... Now my brain hurts
To make a quote from the Earth X comics (I'm such a nerd!):
"...There is no good to be countered by evil. There is only a struggle. There is merely a power play between beings. Good and evil are hollow adjectives. And therefore, the outcome of these struggles is inconsequential and irrelevant to all. There is not a moment in these heroes' histories which amounts to anything. Their every battle is a victory rooted in vanity. Every life saved is a part of some self-serving crusade to undo the effects of the inevitable."
X-51
(but then again, in Earth X, emotions are just a safety function instilled on us by aliens, to keep the human race within certain parameters
)