So Fallout 4 is making some waves by allowing for bisexual and polyamorous relationships. Of course, Skyrim allowed to Dragonborn to marry NPCs of any gender, but had hard-coded monogamy. Early reports suggest that Fallout 4 follows the Skyrim model of vaguely gender-neutral dialogue and no hard-coded restrictions. Still, good to have.
Mass Effect, if you got through the entire series, offered the potential for a bi Shepard with serial monogamy and some flings on the side. Of course, there’s Dragon Age but the less I say about that, the better.
That’s just the AAA world. Transistor fairly obviously had a gay couple and a nonbinary background character. Shadowrun: Dragonfall had multiple same-sex couple, including Glory’s backstory. Shadowrun: Hong Kong has the ambiguous Spider Shen. The Baldur’s Gate Enhanced Editions, a re-mastering of the RPG that popularized romantic subplots, include new lesbian and bisexual plot lines.
The point is that game designers are doing it, largely without making a big deal out of it.