There is absolutely no doubt in my mind that Roger is the best tennis player in the history, because of the well rounded game that he possess. Yes he seems to have a problem against Nadal, which to me is more mental than anything else.
I think the desperation to get past Pete's record also might be catching up on him. So far he has had an ordinary year 2008 (compared to his dream years of 04, 05, 06 & 07).
With 3 gone, Roger would be more focussed to get the last (US Open) major of the year.