1) Ummm....Blake was not even seeded
2) Nor was Nadal
Was Tsonga seeded? And that's even worse since Hewitt faced them in the 3rd and 4th round respectively, Djokovic played an unseeded player in the final.
That often proves nothing. We know Tsonga did well in the final, we know that Blake only started his good streak of 2005-2006, Nadal reached his first Masters final 2 months after that AO and dominated the whole clay that season, won 90 % of his yearly matches.
Nalbandian and Roddick were admittedly tougher and that's it. My point is that his alleged "prime" wasn't too impressive in the actual matches.
That's it and that's enough to prove my point. Who was tougher for Djokovic in 2008 than Roddick/Nalbandian for Hewitt in 2005? David Ferrer? Federer would top both if he wasn't ill and leaking errors from both wings. Tsonga as I mentioned played well in the final but such 1-timers very often lose that final, vide Verkerk who beat 2 best clay courters at the 2003 FO and lost to Ferrero badly in the final.