I'm old school and Clay/Ali Liston 1 in 1964 was my top choice. I like many felt Liston would kill the kid who barely got by a 188 pound Doug Jones and 185 Henry cooper.
My second is Ali/Foreman....Oct 1974. Everyone figured Foreman in 2. HE trained for weeks on cutting off the ring to corner Ali on the ropes and what does Ali do, he goes right to the ropes and Foreman goes nuts banging away. Great finish.
Ali-Frazier 1 and 3
Foreman vs Lyle. 2 superpowers slugging it out. Both were prison bullies and all.
For me it's Tyson VS Berbick