Those guys should beat them however nothing is guaranteed. I wouldn't put money on any of the fights.
Best for best and in a ten fight series, I would pick Ali, Lewis, and Foreman over Vitali. That's it.
Even making the strongest asumption that they fought in a weak era, somebody should have been able to give them a more competitive fight.
Were they good yes. Were they exciting to watch mostly not. But they got the job done. Both retiring healthy, wealthy and wise, which is another positive when comparing them to some other former champions.
Cmon man, you make it sound like they were unbeatable an no one ever gave them an competitive fight. Wlad was stopped by Brewster an brutally koed by Sanders. Even Peter gave him hell in 2 fights knocking him down several times. Vitali was extended into the late rounds by no hopers like Arreola, Gomez an Adamek. British bum Chisora even went the full distance with Vitali an never get looked in trouble at any time. So it’s just crazy for you to say somebody should have been able to give them a more competitive fight. Plenty of them did an more.
I think they both had a lot of talent. They beat some very good opponents and others who weren’t so good. Wladimir’s career had more substance than Vitali’s