Really not sure who Vitali beat to be considered this force of nature h2h boxer... Anyway to answer the question, Ali vs Frazier if we are looking for fighters in or close to their prime. If we throw context out of the window....Ali vs Holmes.
Two good picks for sure, I think we are on opposite ends as far as being fans of Vitali go. I take your point about names on his resume. However in his defense other than the result against Byrd ( where he had completely dominated and won every round) where he pulled out with an injured shoulder. The cut against Lewis in a fight he was ahead in then potentially he would have retired an undefeated champion who then returned 4 years later to become champion again. Phenomenal record.
There's plenty of fighters with records that would benefit from us pretending certain things did or did not happen. The reality is that the best fighter Vitali fought was an older Lewis who didn't look in great shape...and he had what looked like an axe wound opened up above his eye and lost to him. He is my favourite of the Klitschkos and was entertaining to watch, but the rest of fighters considered great h2h wise have got at least 1 significant win. Who is Vitali's best WIN that puts in such high esteem? Lewis doesn't count because he lost that fight. The scorecards are irrelevant because Lewis made them irrelevant.
Vitali lost to the only great fighter he ever fought, even though that great fighter was fat, old & on his last fight. I think the reason his fans figure he's a H2H great, is because he is big & tough. For some people, size rules all. Also, why are people posting Marciano lol? I hardly ever hear him get a mention when it comes to great H2H fighters.
I hope you're joking in the head to head sense. He's not even cruiserweight. Light heavyweight by today's divisions..