Besides the ones mentioned, KOTOR I and II are the only ones I can think of off hand. I think you could do it in both Neverwinter Nights games, but it's been awhile so I'm not quite sure.
As for the reasons behind it, I think they are pretty simple. Most games are made by "white" people, for one. I don't think that it's really even a conscious decision to have white protagonists, it's just a case of using what is familiar to them - it's no more unusual than it would be for black game developers to have black protagonists, or Asian game makers to have Asian protagonists.
Second, a brief glance a wikipedia shows that the 2005 US census reports that 74.7% of the population is "white", while 12.1% is black or African-American. Assuming those figures are reliable and somewhat accurate, I think it would be reasonable to assume that the proportions would represent themselves in other areas, like video games, and that it would also play into marketing and other decisions. Remember that "White" is a big catch-all category as well in the US, which includes people of European, Middle Eastern, Central Asian, and Central/South American ancestry, while "Black" is only people of African (and Caribbean too, I think) ancestry.
It's an issue that's usually difficult to talk about rationally in our country, but I honestly don't think there's really any racism or discrimination behind it (although I'm open to rational arguments to the opposite). The "black" voice in music, media, and politics is very big compared to the actual amount of people it represents, which in various ways gives the impression that it's strange and discriminatory that black people aren't more represented in every form of media. I honestly just think it's an issue of numbers for the most part though - 12% is a very small group of people, after all.