Depends on the game, voice acting if any, animations and poses.
At the end of the day, they are all pixels on a screen.
In my wow days, my toon was a female, because I didn't like the male BE jumping animation and the wavey hand thing they did when channeling a spell.. not because the female was good to look at.
I quite often had to defend myself when I played a female, "I'm playing so I can perve at her", I never thought like that.. so obviously meant the people that brought it up had something deep set in the back of their heads.