Federer is a great player, no doubt. But I think his lack of any rivals really undermines his greatness. He's never pushed, because most of the top players today are mentally weak. There was a really telling exchange after the US OPen. Andy said something like, "If I lose to him in 8 finals that's fine." And Connors was watching and he got livid, and said, "No, it's not." Connors, after getting his ass kicked by Borg in the 78 Wimbledon final, came off and said "I'll follow that ******* to the ends of the earth." Now you have some like Blake saying, "I don't know what to do to beat him. You have to have your best day and hope he has an off day." People mostly lose to Federer before they even go on the court. No one in the men's game has the passion to win just for winning's sake. Now it's all about the $$$.
I'll also say that the posters here who claim Fed is a great net player and can do it but just doesn't want to make me laugh. Fed is a mid-level volleyer at best. He misses routine volleys in every match. He doesn't go to net because he's not really comfortable up there. A great volleyer is someone like McEnroe, Edberg, or Rafter, who could make your jaw drop with their anticipation and skill. Connors was a better volleyer than Federer as well, and Connors, while good, had nothing on the three I just mentioned. Sampras and Becker also put Fed's volleying skills to shame.