I suspect that boxing is in a league all its own. Since it's segregated by weight, it really comes down to who wants it more. That's why we never, ever see rich kids succeed in any weight class.

On a side note, I met Manny Pacquiao in Cebu and shook hands with him. He was running for president of the Philippines at the time (and we were at a wedding with strongly political overtones). My impression was that he had surrounded himself with people he thought he could trust, and that he was uncomfortable with those in higher society. My family there didn't support him - not because they didn't think highly of him, but because they believed that he was out of his element. Having come from poverty, he wanted so much to help the everyday Filipino, but politics requires a very different skill set than does boxing.