Well it all depends. Because most of the time, the characters' sexuality isn't really pointed out in most games. I would only assume that if a character was gay, it would be for shock value or just because it's a taboo subject and would be shoved in our faces. It's like the movie Milk or Brokeback Mountain. There's nothing special about these movies, it's just that the main character(s) are homosexual and was so critically acclaimed because it was not something you see a lot of in movies. I know that if I said that I didn't like a certain game with a gay main character, someone would almost inevitably say that I didn't like it because there was a gay person in it. It's pretty silly actually.
It doesn't make a bit of difference to me, as long as they don't shove it into your faces and make a big deal out of it. You don't see straight characters making out with each other 24/7, so why should gay characters? Knowing the corrupt video game company, they would make the character gay for shock value and free news. That's what happened with Mass Effect (and I am not saying that Mass Effect is bad, it just got free marketing from Fox News) and what probably would happen if they tried this.
So what I'm saying is if it was just pointed out that he/she was gay and they left it at that, then I'm alright with playing it. If a big deal is made out of it, then no.