I direct you to The Longest Journey. Although no really important characters are gay, there are two lesbian characters that serve as minor characters, though fairly important to the story background, who aren't stereotyped. Those two, Fiona and Mickey, are a lesbian couple from England who run a boarding house in the US East Coast city of Newport during the game. Basically, they're the main character's landladies, and they are depicted as being completely normal, regular people, except of course in a relationship with each other. Nobody ever comments on them being lesbian, it's just accepted as a matter of course. Although to be fair, the game is set about 200 years in the future, when it's safe to say attitudes to sexuality will probably be much more relaxed.
Also of note, in the same game, there's a slightly humourous take on the idea when your (female) main character attempts to get into a restricted area by flirting with the male securtity guard. If you keep trying and failing, eventually the guard will say "Sorry ma'am, but I'm gay". Although again, to be fair, given the main character is a relatively attractive young woman, we could probably have worked out the guard's sexuality after the first time he rejects her flirting...
Also of note, in the same game, there's a slightly humourous take on the idea when your (female) main character attempts to get into a restricted area by flirting with the male securtity guard. If you keep trying and failing, eventually the guard will say "Sorry ma'am, but I'm gay". Although again, to be fair, given the main character is a relatively attractive young woman, we could probably have worked out the guard's sexuality after the first time he rejects her flirting...