(listed alphabetically within each tier)
Federer, Gonzalez, Laver, Sampras, Tilden
Borg, Budge, Kramer, Nadal, Rosewall
Agassi, Cochet, Connors, Hoad, Lendl, McEnroe, Perry, Riggs, Vines
Bottom half of the top ten for me. If he can manage a third year as the world's best player and equal Sampras' slam count, then I'd probably bump him up to the top level.