It's not like there are all that many games where characters get an opportunity to prove their sexuality, either straight or gay. Most just shoot around and don't do much.
I presume you don't just want more characters who just "act very gay" or are extremely camp as that is not the same thing as gay.
And another think you HAVE to consider is that while homosexuality is perfectly fine and there should be no shrinking away from the depiction of it, there is still the simple fact that homosexuality is a minority orientation. Only 8-12% of (males at least) are are actually gay so why should we ask that homosexual and heterosexual relationships are depicted equally or anything close to that?
I mean GTA, it even fills it's gay-depiction quota where you have to go on a blind date with Gay-Tom, which at least introduces the audience to how "yeah, gay people do exist". Though you only go on the date to murder the guy, Niko murders everyone so it's equal opportunity brutality.
And the lack of homosexuality in military games like Halo... Hello? MILITARY! Professional misconduct? You can't be chatting up fellow soldiers regardless of orientation, I mean so often one of them outranks the other, it's tantamount to rape or at the very least undermines authority. This goes doubly so for hetero relationships as there are plenty of women in these military forces too.