Gay characters in sci fi are still extremely rare, especially gay males. Sci fi is a lot more comfortable with lesbians, although even then it's often done in an exploitive way.
I can think of several gay male characters in genre TV: Jack Harkness and Ianto Jones in
Torchwood, Sam Adama (and his husband) in
Caprica, Steve Jinks in
Warehouse 13. (And Gaeta on
Galactica, but only in webisodes.) And there have been a number of non-exploitative portrayals of lesbian characters, like Camille Wray and her partner on
Stargate Universe, Toby Nance on
Primeval: New World, Jenny and Vastra in
Doctor Who (well, depending on what you consider exploitative), etc.
And when you say "in sci-fi," I assume you mean film and television -- but that's a tiny, tiny fraction of the science fiction continuum, and generally much more restrained than literary SF. There have been plenty of explorations of alternative sexualities in prose SF/fantasy going back decades. For instance, Diane Duane's
The Door Into... trilogy (aka
The Tale of the Five) has a gay male couple as its lead characters. Although admittedly that might be part of the reason why it didn't sell well enough for her to get a publisher interested in the fourth book.