The only game i can think of that I've played that had a main playable character who was black would be Shadowman. But more importantly I think, is addressing the question of WHY different races/sexes/sexual orientations are underrepresented in not just gaming, but all kinds of media. Being gay and black myself, i long for games that have main characters who i would be able to relate to, not just in video games, but also in books and movies. If you look outside of video games, you'll notice that most movies and books, that are focused on gay/black/ect. tend to be bad, and tend to be horribly cliche. Of course there are exceptions, and it's great when you actually find a something that is genuinely thought provoking, surprising, and entertaining, that you can enjoy on an level that you may not be able to enjoy "main stream" media.
However the problem with implementing these alternative views into the media, is that what ever you're representing, be it a sexual orientation, a race, a sex, a nationality, it tends to overshadow any other part of the story. The experience becomes solely focused on the fact that the main characters of the story are different from the norm. I would have loved to play a Final Fantasy X, where the romance was between two guys, but i can't honestly think of a way in which an idea like this could have been implemented, and not have overshadowed everything else the game had to offer.
We don't live in a world yet, where you can pop in a video game, and have the main character just be black, or be gay, or be a woman, and it's not surprising, or distracting from the rest of the story. There would have to be some explanation (that would be a big part of the storyline) as to why the protagonist isn't normal, and only when we get to the point as a society where these things aren't "out of the norm" will we ever see games where there the protagonist or anything but white males, and it's not the game industries fault, it's just the way the world is.
When we finally don't reach that point, we won't even have post like these, cause it'll be just another video game, movie, book, tv show, nothing special, cause we're all the same.