Almost impossible to narrow it down to one but I'll try. The ending to this fight put it over the top. After 9 rounds of toe-to-toe savagery, Corrales and Castillo produced the most memorable round I've ever seen. Even after watching it dozens of times and knowing what's coming, I still get goosebumps and jump out of my seat every time I watch it.
even though there's many great fights throughout history, MAB vs Morales is the best i've ever seen. that truly took my breath away for the whole 12 rounds.
Simply an impossible task. Started listing them and could fill a page easily. Then it comes down to what styles appeal most and people's opinions vary on that too. Best short fight IMO was Hagler vs Hearns though, and people might think other short fights topped that too.
Meh hard to say Thrilla in Manilla saw the end of surely the greatest rivalry in boxing history in one of the toughest grueling fights in history.
How about Ali vs Frazier I? Does anybody put Ali Frazier I over Ali Frazier III? Obviously they both were classics, but considering Ali was coming back after being away from the sport for so long, considering it was in MSG, considering Frazier knocked down Ali and won, and considering it was just so classic. The Thrilla in Manila was a grueling war, but their first fight I felt had more of a big fight feel to it. And the outcome was so shocking. It's hard to narrow it down to just 1, but I have Ali Frazier I and Ali Foreman both near the top. It's hard to put a modern day fight ahead of those classics.