1) Wlad and Lewis (tie)
Wlad never defeated a fighter as good as Vitali, but otherwise he fought and stopped a lot of prime opponents who had never been stopped before and/or were undefeated.
All the people Lewis fought people stopped except for Vitali had been stopped before. Holyfield was past his best and Tyson was past his prime.
Liston has only two wins of note over Patterson. I rank Vitali higher because of his longevity (the only HW to hold a world title in three different decades) and relative consistency. Both had bad moments: Vitali quit against Byrd when he was injured, but Liston quit against Ali without an injury and in the rematch took a dive.