That is true. I think without that insane Madrid match, Nadal quite possibly wins RG 2009 and maybe even Wimbledon 2009 (and that is not only 2 more slams but 2 less for Federer and a 4 slam swing). There are so many ways things could change. Also it could be argued he pushed himself so hard to get back on top of Djokovic again in early 2012 it led to his injuries that caused him to miss 2 slams.
Regarding the 2008 Australian Open I agree, and that was what I meant when I said 3 (before speculating on chain effects related to Djokovic like the ones above) would be best case for Nadal and worst for Federer. I do think Tsonga was playing a higher level than Roger at the 2008 Australian Open for sure, but he was arguably even playing at a higher level than Djokovic and still lost, and nerves were definitely a factor in that final. Obviously Federer had no chance of winning events like 2012 RG or 2010 U.S Open over Nadal, but you could argue he had a shot at the 2008 Australian Open and even 2011 U.S Open perhaps, along with the 3 fairly safe ones of 2011 Australian, 2014 Wimbledon, 2015 Wimbledon. Whereas with Nadal while he could well have won all 3 slams he lost to Djokovic in the final, you could argue Federer having a chance at the 2011 U.S Open and even Murray at the 2012 Australian Open. However since Nadal was a combined 4-0 vs Federer and Murray in slams from 2011 French Open-2012 Australian Open I would back him for those, but I guess one could argue atleast.