I am not sure it would at his peak. Jeffries continued to improve right up to the point where he retired, particularly in terms of boxing and finishing ability. The prime Jeffries was not the version that won the title or the version that went 23 rounds with Corbett. He started his title reign with little more than his physical assets and gradualy refined his technique untill by the time of the second Corbett fight he was the ultimate fighting machine. By the latter fights of his career he was not needing 15 rounds to put people away or getting outboxed by anybody. If we look at the last 3-4 years of Jeffries title reign: Joe Kennedy 2 rounds Gus Rhulin 5 rounds Bob Fitzsimmopns 8 rounds Jim Corbett 10 rounds Jack Munroe 2 rounds Clearly the 15 round limit would not have helped these guys.
This is how I see it. Jeffries got better as his career went on. Some say we never saw the best version of Ali from 1967-1969, it is plausible that Jeffries never peaked, and would have been even better had he not retired in the years of 1905-1908.
Dempsey was past his peak when he fought Tunney but both fighters are underrated. I think johnson, dempsey, louis and tunney would all be at the top.
No Wills? No Jeffries? I think both should be above Dempsey and especially Tunney who just has a too thin resume to be considered a great hw.
Dempsey above Tunney on the all-time list, maybe, but I firmly believe Tunney decisions any version of Dempsey.
Fitz and Corbett were old,Kennedy was kod early twice before meeting Jeffries Maher did him in 2 rds and Van Buskirk in his first fight kod him ,he was kod in 4 rds a year after Jeffries stopped him by Jack Johnson ,Munro was nothing.Jeffries was probably in his prime when he retired ,but I think you read too much into him koing an over 40 Fitz and a Corbett who was well into his 30s.Ruhlin had been kod a year before meeting Jeffries in 6 rds by Fitz .I think the earlier poster was correct ,Jeffries ,against the better fighters needed time to wear them down 15 rds would not have favoured him at any stage of his career.
No Tunney has the right boxing style and ring intelligence to beat bigger or harder hitting fighters. Dempsey at his peak would not be underdog against any. Johnson is great, louis is proven great. So they are my top 4. Wills could be a wild card as i don't know a great deal about him or his style of boxing? the boxers who hit and move i favor more against the bigger heavies. the lighter swarmers could end up smashed to pieces like frazier did against foreman.