Dominance.

One of the more common arguments among sports fans is who is most dominant in their sport, ie: Lance in cycling, Tiger and Annika in golf, Tim Duncan in basketball, etc. I think the case can easily be made right now for Rafael Nadal in tennis: at the tender age of 20, he has just stared down a modern great in Roger Federer and came back from a set down to win his second consecutive French Open (his sixth win in seven meetings, fifth straight over Federer), his 17th title overall, and now 60 straight wins on clay. This kid's got a gleam in his eye.