I am a male, and I don't think that I have any particular aversion to playing as a female character, but most of my online characters are mysteriously male (maybe 90%).
By contrast, in tabletops I'm much closer to 50%/50%, and in video games where gender is a choice, it's probably closer to 10% male.
I'm pretty sure in video games it's because if I'm going to watch someone run all over the world, she may as well be pleasant to look at. Probably a touch chauvinist, but true.
But I can't explain the other two. Never really thought about it before now though. I'm really sort of curious about it now though.
I'll probably play a female character next just to see if it tells me anything about myself.