this is just astounding;

from the australian open in 2004 through this year's wimbledon, there have been 63 grand slam finals
federer: 19 wins
nadal: 18 wins
djokovic: 16 wins
wawrinka: 3 wins
murray: 3 wins
gaudio: 1 win
del porto: 1 win
cilic: 1 win
safin: 1 win
so, federer, nadal and djokovic have won 84% of the 63 grand slams contested in 16 years. that is absolutely bananas.
if you shrink it down to 2004 to 2010, there were 28 grand slams, federer won 15, nadal won 9, djokovic, safin, gaudio and del porto each won 1. federer and nadal combined to win 86% of the grand slams in that 7 year period.