For me it's between these fights. Pacquiao - Barrera I Pacquiao - Cotto Mayorga - Forrest I Hopkins - Trinidad Morales - Pacquiao I Hopkins - Tarver
Here come the excuses for Cotto...sheesh. The most I'll give him is that he wasn't the same mentally. His physical toughness and skill were still there, but is it Pacquiao's fault that Cotto was emotionally scarred in the Margartito fight? Look, I stopped just short of saying it was the definitive performance of the decade, but it was surely a notable performance, and shouldn't be ranked no lower than 3 or 4 by anyone...even Pac haters.
You might not agree that Pac - Cotto is not the single best performance of the decade. But it's definitely up for consideration at the very least. No doubt.