I've never seriously played as a female character. I usually like to make my RPG characters have some aspects of my RL self (but not exactly the same - more or less good, evil, crazy, warrior/magically inclined, etc.) and I try to immerse myself in my character and I've just never felt inclined to make a female char.
I've always wondered what the dynamic for males playing female characters was, but figured it was some variety of demographics of either transgender exploration/curiosity or guys wanted to oggle female backsides while playing (or at least have something pretty to look at). Most of the male gamers who were straight played male characters with a few exceptions and
all the women gamers I've know have played female characters when the option was available. I've only known a couple of guys who ever played female characters (more promiscuously than a woman would normally play them) and I figured they were either gay (don't mean in a negative way) or they were straight and just got off on making the female chars do crazy stuff. The latter one is probably more likely.
Then I noticed about the time I started played some MMORPGs like Everquest (a looooong time ago) or
watching people play WoW, it seemed like alot of guys started playing female characters for some reason. I made fun of it at first, and then started to accept it, but never really understood why they did it, especially since some guys who play girl chars in MMOs take offense to being treated or referred to as female. It kinda turned me off of role playing in MMOs because someone would flirt with a female character as an 'in character' thing and someone would sometimes say something like "dude, you do realize I'm a guy?" And so, another great RPG romance is shattered.

I know the demographics are probably alot different for a single-player RPG.
Anyway, It's been interesting reading all the perspectives on this and surprising that most people have been able to discuss it civilly without alot of immature arguments. It has given me a little better of an understanding.