He has lost to no names at Wimbledon, true, but i think you need to accept that he was injured during one Wimbledon a couple of years back, how serious the injury was we don't know and it's pointless speculating as we will never know, but he did have an operation shortly afterwards that kept him out for around 7 months. That alone suggests it was at least a niggling injury that he had to tolerate during that tournament. That said he has also won Wimbledon twice and reached two finals against arguably the greatest grass court player ever. He may not have dominated on grass but he has most definitely proven himself to be amongst the best of today quite simply for beating Federer in his prime in a final at Wimbledon and also taking him to 5 sets on two other occasions at a very early stage in his career.
Perhaps it is slightly presumptuous to say that he would have won 2 or 3 more slams, but as i said above it's a valid argument to claim that it is fairly decent possibility that he would have. Weren’t he seriously injured in an Australian Open match a few years back against Ferrer which he eventually went on to lose? He was also injured in the Australian Open final this year (although Wawrinkwa was playing brilliantly so a win there was by no means a certainty). He has also completely pulled out of 1 Australian Open, 1 Wimbledon and now 2 US Opens. That's a total of 7 slams where he has either pulled out completely or has not been fully fit to contest to his full potential. Perhaps it is slightly presumptuous to claim that he would have won a couple more slams, but do you not agree that there is a very decent possibility that he would have?
All that said, I’m not claiming Nadal is the best ever, as the ‘best ever’ debate is always a nasty one as you have the age old ‘you can’t compare generations ’ argument to contend with. But as far as this generation is concerned, I regard both Djokovic and Nadal to be better than Federer. But at the same time I also understand the reasonings behind why people feel Federer should be regarded the better of the two. As I said in my above post, the debate is far from cut and dried, there are valid arguments for all three. I just personally slightly lean towards Rafa, then Novak (although my opinion with those two changes fairly regularly) followed by Federer.