What is the greatest rivalry in boxing history?

Comment below which feud takes the top spot and why.

Ali/Frazier is tough to top, but one that isn't mentioned as often was also special, Duran vs. DeJesus.

Gatti vs Ward!

Really hard to look past Ali vs Frazier overall. If I was to exclude that and go more modern, Pacquiao vs Marquez

Ali vs Frazier feels obvious but if I can loop both generations into one, Benn vs Eubank is a rivalry that was passed down to me.