From a historical standpoint, I would say Louis over Schmeling, as it essentially became the U.S. vs the Third Reich, and partially debunked the theory of a superior race.
Louis beating Schmelling was epic and world-changing beyond anything we can imagine today. It went way beyond boxing. Nothing since even remotely compares.
I've tried to get him to change that order. It's easily the best of any Fab Four (Five, really: Benitez) win and probably top three all-time, period.
Such a strange fight... Douglas getting KD'd for 13 seconds, Tyson with no corner or qualified cut man. No bucket of ice...Hmmmmm???????????????????? Howa bout that warm water balloon? Think it's just negligence on Don King's part?