I'd always thought that playing games with only the intention of playing an idealized version of oneself to be more creepy than the idea of just playing any character for the heck of it.
Guys who absolutely refuse to play female characters creep me out. It's as though they actually project themselves into the game. Something I find a bit off, especially since I prefer either games that star a character with a personality other than something I define myself (usually, pre-existing characters are more interesting and easy to give a damn about than nameless, faceless player avatars) or games that put me in a position detached from the action, my input reserved for the moments when I send an order or two to my troops.
The idea that one should only play idealized versions of oneself in games feels strange, to say the least. People who think poorly of people who play characters of different genders are also plenty creepy; these are the kinds of people who either read way too much into things or are trying to find actual women on the internet to hit on (and get suddenly defensive when revealed that they're hitting on a guy).
But honestly? I don't care what gender my avatar is if it's in first-person. I have a gun, and I'm there to use it. Not to fiddle around with gender issues or address male gender insecurity.
And does "Genderless deathbot" count as a character of a gender other than one's own? Much rather play a deathbot than a fellow or lady, anyday.
Mmm. Deathbots.
EDIT: Though "lousy voice acting" is also a good reason to choose a character of a gender not one's own, too. Mass Effect was cringe-inducing when playing as male Shepard, but really engaging and immersive when playing as female Shepard. This is because it's a dialogue-heavy game, and if you have to listen to your character talk all the time, it better be voiced by an actor who can act.