It'd have to be Foreman Frazier seeing as that was the most dominant and conclusive of the lot. Probably the highest quality matchup too.
Foreman vs Frazier and Bowe vs Holyfield are two best. Then it's Holyfield vs Tyson, then LL vs Holyfield (who was much worse than the prime version that Bowe had beaten), then Wlad vs Peter and Bowe vs Golota is the worst one by far