Been thinking about that a bit lately. People talk about the dearth of shooting guards these days, and I think a lot of it is just how the positions have been redefined a bit. Saying there are only 5 types of basketball player is a patently absurd assertion, given all the different possible combinations of body type and skills. If the Thunder had a PG like Parker or Rondo, we'd be thinking of Westbrook as a Jordan-type player, not comparing him to the great PGs. But they don't, so he and Harden have to play that role.
He's still really f'in good at it, though. Bottom line is that he can break down any defense, and good things almost always come from that.