Russell Westbrook is the best athlete to play point guard in the history of the NBA. In terms of size, explosiveness, and overall physical talent, no one who has ever played this game at point guard can touch the Oklahoma City Thunder star on that scale.
Importantly, his disposition to dominate the game from a physical perspective -- always looking to attack, rebound, or run, for example, is the key that takes him from being an elite-level athlete to perhaps one of the league's top-5 players. In simple terms, he plays the game like a power forward who happens to be the team's primary ball handler.
Even his recent knee injury and surgeries have not been able to slow him down much in the action we've seen him in thus far (he is not finishing great yet but that part of his game should return soon). Everyone frets over his eagerness to take long shots and jumpers, but what's interesting about him, though, is that his worst habits are a big part of why he is so good.