Well, I don't think he will win as many grandslams as pete or even andre. He has beaten many top guys in the regular tournamens. However, I think in his grandslams victories, he has not faced the top contenders like federer, safin, or haas. If he beats these guys consistently on his way to win more grandslams then I will admit he is a phenomenon.
But I don't think he will last that long in the number one spot.