It depends how would you define a game with a gay lead. And don't say "the definition is right there, you moron!", cause I think it all depends on what part of the gay lead spectrum the game would be in.
In many games, the protagonist's sexuality isn't even mentioned, and I don't think people care about it at all. If pushed, they'd probably say it's "straight", for no other reason than, 95% of population being straight, this can be easily called "norm".
If it's mentioned as part of backstory, or a few times within a game, but has no major influence on the story, I don't think anyone would care. Maybe a few anti-gay people would protest, and a few pro-gay would proclaim it a success (and that could marginally affect sales), but otherwise, I don't think it would matter.
If the game's built around the character being gay, frankly, I doubt you can make a good game out of that. Centering the whole plot around the character's sexuality... I don't think you can squeeze a good plot out of that.
On a similar note, if the game's made for no other purpose than to make a statement, I wouldn't play it, although I imagine people who would just to show how they "go against the flow". A game repeatedly bashing me over the head while proclaiming "homosexuality is good, embrace it!" (as well as one doing the same, only claiming homosexuality is bad) just wouldn't make it for me. I don't expect sermons from a game, I just want to play it and have fun (which doesn't have to be mindless fun, but please, save the preaching).
By the way, how would you define the gay character, in game? There are some gay people who behave like they were taken straight from a sitcom, but making a character like that would probably alienate people from both sides of the debate. So, how do you actually MAKE a gay character? Seeing as the only defining characteristic is a preference for the same gender, how would you go around constructing a gay character? If their orientation is only mentioned a few times, then I don't think anyone would care. If you decide to throw in a few gratuitious homosexual sex scenes, then I do believe a lot of gamers would feel grossed out, and no, this has nothing to do with "gay-hating". Just a scene with "two guys kissing", that I think depends on each individual gamer.
To round it all up, a good game will be good, a bad game will be bad. If the only selling point of a game is "it's main character's gay!", then it would probably be on the "bad" side. If the game's interesting, with a good plot, and the romantic plot is constructed well (so far, 99% of the games seem to take the "first we frag, then we shag" approach), then anything short of homosexual erotica would probably fail to put gamers off.
A long post, and an awfully written one, but just one more point I wanted to make. I don't think comparing gay leads and black leads is the way to go. A black character - well, that's just the same as a blue-eyed character, a big-nosed one, or, well, one with 10 TIMES AS MUCH MUSCLE MASS AS I HAVE. Skin colour is an outward characteristic, and does not affect beliefs, morals, or behaviour. A gay character, well, that one's pretty much DEFINED by differing in worldview. That's why, I think, it would be difficult or plainly impossible for most people to identify with a gay lead.
