Lennox vs Vitali i'd rate a toss up. (remember Lewis's chin) Wlad vs. Lewis, unless Wlad takes Lennox out early, he gets destroyed.

Bowe vs Wlad, i'd give an in shape Bowe the edge, but the Bowe that fought anyone except Holyfield would get KTFO. Vitali would give Bowe a beatdown.

Prime Tyson would have knocked out Wlad, but i'd favor Vitali by late round KO.

Larry Holmes would outpoint Vitali, and KO Wlad.

Prime Ali would have seriously clowned Wlad, and stopped Vitali, very likely on cuts.

The George Foreman who annihilated Frazier would have knocked out both Klitschko brothers.

Keep in mind, that aside from Lewis, neither Klitschko Bro has fought anyone on the same level as prime Bowe, Tyson, Holmes, Ali, or Foreman. Also keep in mind that you never know how these fights with the K-Bros might go, both Bros are big, tall, powerful men, who stay in shape and have good technical skills, don't underestimate them.