While I believe a lot of it has to do with work ethic, determination, training, etc.. there are still genetic things that play a pretty large part. Lance Armstrong has a larger than normal heart that helps with his endurance. You can't train your way to being taller or having longer arms which really helps you in basketball.
So while it doesn't guarantee success that are definitely genetic factors that can give you an advantage over others.
Agreed, however Lance Armstrong is not the greatest example, seeing as he cheated throughout his career. However I will concede that being genetically predisposed to something can give you a leg up, however that's not the same as natural talent as I state it.
I am addressing your point, in part, in the next in the series :-)
Cg