The only thing that matters to me, as far as in-game marriage goes, is if it offers any benefits to the players. Such as, shared housing, shared inventory, shared gil, etc...

Other than that I don't care if it's same gender or not. You would think people would be more upset with cross-race marriage for other reasons... taru and galka (lalafell and roegadyn).

Actually, I take that back... I would care, and would be more upset if I can't just marry whoever I want just because I chose the wrong gender. Such as, having to re-roll in any game just because you can't unlock a portion of the story because of a different gender... Although slightly different for single player games, it'll receive same negative feedback if there's any benefits attached to marriage.