Racism inherently starts with the assumption that there are taxonomic differences between different groups of people.
The shows, videogames and other things you listed do in no way imply such a thing.
There is merely the fact that these games/shows are aimed at a group that consists mostly out of white people.
It's like Erimgard said most people can identify better with a person of their skin color, much like males tend to identify themselfs with male character and females with female characters.
You see more male video-game protagonists, because there are more male video-gamers then female video-gamers. (all though female gamers are increasing)
It's much the same princip with videogames and TV-shows, there are more white people watching TV then there are black people. That's why tv-producers, for the sake of moneymakeing, aim there shows at white people.
There are however also shows that are aimed at black people, and most shows/games include a black character to please the black viewers.
Like Soul Calibur had Zasalamel:
http://upload.wikimedia.org/wikipedi.../Zasalamel.jpg
He was an awesome character and had a very deep character.
Finally I would like to say something about the Zelda games:
The Zelda games take place in a world that has a medieval feel to them. The medieval time, as it's seen in Zelda, is something that makes people think of europe. Not many black people were seen in europe during medieval times, thus it would seem strange to include many black persons into the game.
To conclude:
I don't really think that these are cases of raceism, since nothing in these shows/games suggest that white people are inferior to black people or visa versa.