Boxing rivalries in general, at the elite level, are wildly entertaining. See these modern trilogies for proof: Gatti-Ward (okay, so this is not "elite level", but it more than makes up for it in intensity), Barrera-Morales, Pacquiao-Morales, Jones-Tarver, Bowe-Holyfield, Corrales-Castillo (the 3rd non-bout's weigh-in makes it a trilogy of sorts)
I'm probably forgetting some, and that's just for the last 10 years.