Depends on the RPG. If it's one with built in characters, well, you have no choice, so run with it. But, if we are talking about ones where you make your own character (like Mass Effect and Elder Scrolls) then it comes down to one question:
"Do the males in this game look like steroid-overdosing, brainless twits?"
If the answer is YES (as is the case in most MMOs) then I roll a female character. Let's face it, if you are going to be staring at the rear end of someone for hours on end, it might as well be a cute one (unless it's like my step-brother, who made a female character for Dragon Age, then promptly donned plate mail armor).
To me, RPG characters aren't a representative of me personally. I don't make them out to look like me or behave as I would if I were in that situation or environment. It's just a character, though I do, sometimes, become attached to these characters I've spent dozens of hour helping them through their adventures.
On the other hand, if the males aren't modeled after Lou Ferrigno's byproducts, and it's in a situation where I wish I WAS in (like a galactic hero via Mass Effect) then I will always chose a male avatar and tailor it to resemble myself, if possible. Gotta feed the ego some days.
