Trek really, really dropped the ball on this one- obviously a gay character should be in any future series, but when they had a chance to really make a difference and be progressive and forward-thinking (when DS9 and VOY were airing, basically), they decided to sidestep the issue (with the exception of Rejoined and The Outcast, of course, which were both excellent). Even if they do have gay characters in future episodes of some hypothetical future series, they will be so far behind the curve it will be laughable.
That said, it is an extremely tricky issue to tackle and I can see why the predominantly white male writing team behind all of the shows were wary of introducing it, since it would be under immense scrutiny and any misstep could be horribly misconstrued.
A big part of Riker's character IS his heterosexuality. I think that is fine and we know people like that in reality. Most of my gay friends do seem gay. Some (a minority, certainly) of them are outrageously camp in a way that would seem totally OTT if you saw it on a TV show (as the Jack character was on Will & Grace), particularly a show like Trek where most characters are understated or, god forbid, actually quite bland. Most of them are not camp but are quite straightforward about their sexuality- you'd know they were gay after talking to them for 5 mins. I'm assuming that we're talking about this sort of representation on Trek (since 'campness' is so era-specific, it wouldn't really wash in the future [not to say that you can't have camp characters, like Lwaxana, in Trek]), where a character doesn't seem that different to the other characters, they are just sexually interested in same-gender characters. How would this be teletyped, on the show? The best thing you could do is play it directly, as they did in Rejoined, not make a big deal of it. But it would still have been a big deal to the audience, since it was this new thing, and everything would have been a statement. I think they can and should have done this- but it is somewhat understandable why they did not.
Anyway, in my head, Geordi, Garak and Harry Kim were all totes gay.