1. Tim Duncan
Tim Duncan has led his team to four championships, three during the decade in question. He scores efficiently on either block, is a monster defender, rebounds like few others, draws huge amounts of attention when he has the ball offensively (something Kobe and KG, for all their gifts and for all the double-teams sent their way, just can't compare to), and he wins games.
Has he had great teams around him? Sure. But he's been better than everyone else.
If you really think about it, if you really deal with the game on the level it deserves, you know he's been the best. Really, it shouldn't even be a question. Tim Duncan's been the best player of the last decade.