Was probably already said, but the likely reason that no one has made a hubbub over gay marriage in Skyrim and the Fable series is because there isn't any real weight behind the relationships. In Skyrim, you just wear an amulet and you go talk to one of the marriageable NPCs and hey, they'll marry you. Congrats, you got a little vendor in your home now. No sex, no mentions of the relationship, the guy/gal will just call you 'my love' now.
In the Fable series, almost all the relationships you can have boil down to make their approval bar of you be high enough and they'll marry you, regardless of morality/gender/appearance/anything. Most anyone is interchangeable with the next ten blokes, and for sex all you get is a black screen with a few grunt put in (although in Fable 3 you do get a bit of silly music and very over exaggerated exclamations of joy). When married, you just have someone around your home who'll either complain about how the house/you look, they want money, or how you're not there enough. And you can get married as many times as you want with as many interchangeable people as you want.
So yeah. People only complain about same sex relationships in games if there's substance to them.