Resurrecting a dead thread because having two threads on the same subject on one page is... unnecessary.
Most games I'll play based on who I want to create. I think about the character, not just the gender, though I do tend towards female characters, especially in 3rd person games, for aesthetic and system-oriented reasons. First off, I do find females more pleasing to look at, and secondly people with a smaller frame take up less screen space.
This extends to tabletop rpgs as well. If the character as it develops seems to be more useful as a male or female, they'll be a male or a female. Though this time I tend towards males because I tend to be a pretty all-out actor in roleplay, and I don't trust myself to act out as a female well enough. I'd just rather be better at being before doing this.
And then we follow that with online games. I play EVE Online as Lily Shahn, acting in-character and in-role. I explain my inability to speak in comms as an "embarrassing vocal issue" - this will save having to force people listen to me transition. I've had someone try to call me out as a boy before, which was fun.
So, to those who are worried about passing or coming out, how do you portray yourself in social games?