It is irrelevant to me, but in RPG games where you are allowed to make a character and are encouraged to immerse yourself in a game universe I prefer to make an avatar that is similiar to me. I choose a male character just because I am male in real life, is simple as that.
I really can't think of many games where a female character in place of a female or vice versa would really detract from or benefit the game experience. The new Tomb Raider would be just as good if Lara Croft was Larry Croft, and Deus Ex HR would still be a masterpiece if Adam Jensen was replaced with Adana Jensen. It is the gameplay of Tomb Raider that counts, and the awesome story/gameplay of Deux Ex HR that truly matters.
There may be some exceptions though ... Duke Nukem would be... different as a female. The gameplay would not change I guess, but it would have to be an over the top misandrist in place of the over the top misogynist that is Duke.
Another example would be ... maybe Silent Hill 3? Heather Mason was about to birth a demon ... a man can't really be pregnant with a child/demon/anything ... except for that awful Schwarzenegger movie.
