It has gotta be Lebron James.
He can defend, pass the ball, take shots, drive, get to the line, take over a game..
He's the complete package. You don't see him losing to his opposition going head-to-head.
To begin with, CP3 is non-existent against someone like D-Will, so, I really doubt if he could really be considered a clear-cut best PG in the league, let it be the best overall player.