Interestingly enough, i believe the Fed-Djoko rivalry would have been the best, if only they got to play each other in finals instead of semis. '11 FO and '11 USO were classics, with honorable mention to '10 USO as well.
Fed-Djoko is actually an even bigger contrast than Fedal, because Fed and Nadal actually have similar strengths, they just execute them differently. They both rely on FH's, movement, slices, plus Nadal has a strong net game thats underrated.
Whereas Fed-djoko its a FH vs BH, Serve vs Return, Net game vs Pure Baseline. And you actually don't know who's going to win, HC's they're both awesome, Clay they're both awesome. Grass is the exception.