There should be separate polls for 1st serves and 2nd serves... and by 1st serves I don't mean something Nieminen does
Anyway, this discussion is not complete without this link
Although it doesn't tell the whole story... Nadal is, indeed, a good returner but his score is somewhat inflated by all those points he won in his plethora of clay matches, where 'returning' is mainly irrelevant compared to the subsequent rally in which Nadal usually dominates.
Best returners of fast 1st serves seem to be Murray, Ferrer and Federer. 2nd serve I'd usually pick Nalbandian but it's a long time I've seen his best. Davy and Nole also seem to punish weak serves pretty harshly. Federer is surprisingly meek returning 2nd serves, probably because they almost always go to his BH side. Poor Fed