First off let me say this. I was never a fan of tennis, until Federer showed up. I never actually watched a match in the wee hours of the morning in the US, until Nadal showed up. I think Federer is the classic, has all the intangibles and skill. Meanwhile Nadal is the flashy, athletic, younger, endorsement cash cow.(with skills to back it up, though)
Federer is the best ever. Its not his fault he was head and shoulders above everyone else for a long period. Look at Michael Jordan. However, I think right now, Nadal IS the best. Nadal is younger, and I also think he is going to be on top for a while. At the end of both careers we'll be able to comment on who is the best ever.
Federer has every shot imaginable in tennis. He can place the ball in places people can't reach or arent fast enough to get to. That is, until Nadal showed up. Nadal's skill set is very close, but what pushes him over the top is definitely his speed. He can get to the spots where Federer places the ball, and I think he's also starting to get in Federer's head. I think it psyched Fed(sorry started getting tired of typin the whole thing), when at the Australian open they were coming through the tunnel, Nadal was right behind him. He probably felt him breathing on his neck. lol