A characters sexual orientation shouldn't be an issue in a game, maybe only in a RPG and then you should have to chose which way to go, and I most likely wouldn't play a gay char.
So I guess no I wouldn't play a game with a gay main character.. why ? because it would probably feel forced, I mean ... what is the point of making him gay ? does that make the story better, is the character better because of it ? .. having a gay character just for the sake of him being gay is dumb and pointless, and it probably wouldn't be a very good game if it centers around the fact that he is gay.