Meaning, could anyone better Foreman's KO 2 over Frazier? Or Could anyone have controlled Holyfield as well as Bowe did in their first fight?
No. In order for that to happen, the landscape of the HW division would have to change. Foreman's win was significant and Bowe put on the performance of a lifetime against a champion with a heart as big as the whole town. I assume this is a HW thread, if someone steamrolled Wlad or thoroughly outboxed him that would be on the bottom of the list. In WW I guess if Maidana came in and walked Money down and KOed him that would be historic. Don't forgot those great wins you mentioned were instant classics that got more impressive with age. Some great wins are viewed as flukes at first.
It depends on how far you are willing to stretch a point or travel in time. I think it's probably that Holmes could have done a better number on Sullivan than Corbett did - but it likely wouldn't have had the same "flavour", I suspect the fight would have been much shorter but with a probably change in fortune, maybe more than one. I think it's reasonable to guess that a prime Tyson could have gotten Fitzsimmons out of there before Jeffries. And of course there are many great heayvweights that would have put Jeffries away before Johnson did - but then, this was hardly the point on fight night, was it? Complicated question. Liston and Ali are perhaps the best answers to your specific example, but I wouldn't bet on either.
Bit off topic here but was Foremans first win over Frazier viewed as a fluke? Also, in the rematch was Frazier expected to turn the tables?