I think it depends on whether by the "best" you mean the best potential person, or best current person. At the levels these sports are competed at now, I think

I think it depends on whether by the "best" you mean the best potential person, or best current person. At the levels these sports are competed at now, I think natural talent by itself can in no way stand at the top. It takes natural talent and then dedicating a significant portion of your life to cultivating that talent. So, does the potential for a faster runner exist out there now? Undoubtedly (this is a safe bet, since records are still being broken). Is some street ball player going to walk in and dominate the NBA, or some weekend runner going to storm the Olympics next time? I doubt it.