Actually it;s CP3 in my opinion but now that I have you here I'll explain my theory on the best PG's.
Best PG: CP3, Rondo, Nash
Best scoring, takes a ton of shots, might get assists, and happens to play at the 1 spot: Rose, DWill, Westbrook (DWill is a stretch but for the argument, he fits more here)
My point is that the PG is more a floor general, ball thief, assist machine, who really gives you a bonus in points (Jason Kidd is a perfect example here.) I believe Rondo is the best or second best PG in the league. While I would probably take a Rose or Westbrook over Rondo in fantasy or a pickup game, if I had a good team already, I'd look for a real PG who can make the rest of the team better.
Not a knock on the Rose's or Westbrook's, they are who they are because of the team they are on. Those two guys wouldn't work in a Lakers or Celtics team (kinda why the Lakers would like a CP3 over a DWill or a Westbrook)