Liston and it's not even debatable. He beat more contenders both before and after his prime. Liston steamrolled through the division beating most of the noteworthy names while patiently waiting for his title shot. Bowe's resume is incredibly top heavy with the Holyfield wins and not much else other than the okay victories over Gonzales, Hide, old Tubbs, etc. For a man with all that talent and size, Bowe had a fairly lackluster career and didn't even reach 80% of his full potential and he missed quite a few of the best men of his era.
I say Liston because he beat many of the top heavyweight names of his era. Although, Bowe's win over a prime Holyfield is nothing to sneeze at, as prime Holyfield is arguably better H2H than anyone Liston beat. I would rate prime heavyweight Holyfield as a tougher opponent than Floyd Patterson H2H. But Liston consistently beat the top names of his era.
^This^ And another reasons. Liston convincingly dominated both late fights with Patterson, while Bowe lost the rematch with Holyfield. Liston realistically should have become champion a few years earlier, and in such a scenario Johannson would not have been champion at all. Liston #11 Bowe #14
Liston beat all of the best of his era he could get his hands on. PattersonX2, WilliamsX2, Foley, Machon, Valdez... Bowe only beat Holyfield, missing out on fights with Lewis, Tyson, Foreman, Holmes, McCall, Mercer, Moorer, Morrison... They weren't all his fault, but some of them, most notably Lewis, were ducks.
Who are these other ducks exactly lol? I’ve seen that Bowe Lewis video, signed to fight in 95 and then Lewis declining Bowe in 96 I heard… interesting.