Wow this could get real ugly...Iam going to take a stab(not an OJ Simpson reference) at this...Remember you mentioned only sports which are televised and there are sports that are not on tv which they are not the majority...
I think it is both gentetic and social. Genetic I can not prove since I have not done studies and the such, but it just seems like the the major sports are a majority black. I can only make my opion from what I see. I bet if someone was able to do a census of ALL professional athlets and the sports competed in the olympics the ratio would be closer than you might expect.
The social aspect could be that for the black community sports is a more accesable way out of poverty, thus giving them more motivation and dedication needed to rise to the level needed to become professional athlets... Like I said I would give it a stab...