I think with the HW division as it is, all three of them had/have significant chances of holding one of the ABC world titles. Stevenson would've been the best without question. As for Jerry Quarry, he would've been better suited at CW where he could've really mopped that division up. I'd give him a chance against the lumbering technically flawed and one dimensional Sam Peter easily. If Chagaev from the Skelton fight shows up, I'd trust a decision win over him as well. It all comes down to whether he could go 12 rounds without cutting.
I 100% agree, only thing I would change is from "could" be a champion to "would" be a champion today. Undispiuted champ at that. He would knockout wlad IMO.
Stevenson was the real thing, in any time in any country, he would have been competitive. Quarry was better than Cooney, but I don't think either of them was much more than big, tough guys.
In my opinion Quarry would be a cruiserweight champion today. The pre-Holmes fight Cooney would be competitive and possibly a belt holder. Stevenson had the tools. He would have been competing during the era of Ali, Holmes, Foreman, Norton. Of the three I think that Quarry would have the best chance at winning a title.
While Stevenson certainly looks impressive, you have to remember that what you see is an experienced, mature man vs young upcoming, often not even 20 year old fighters. And how did it translate for Biggs when he beat Lewis in the amateurs and then fought in the pro's? How far did Tillman go after looking impressive and twice beating Tyson in the amateurs? How far did "the next undisputed 6'5 240lbs southpaw champion with fast hands, Audley Harrison go? Take that in mind before you say with certainty that Stevenson would've been so great. Chin, stamina, folding under pressure, fighting experienced and older opponents, the rougher pro game, living the high life, etc... those are all factors that have made many a great amateur fail at the pro's.