Contemporaries who've seen Sullivan, Jackson, Corbett AND Dempsey, Tunney, Louis that compare them?

Thought it'd be a good idea to dedicate a thread to contemporaries who've seen the eras and how they've compared the eras, do you have any?

Here are a few;
Jack McAuliffe

“At his very best Sullivan would have given Dempsey a hard fight, but Dempsey would’ve knocked him out. It would have been a short and sweet fight, I’ll tell you that, but Dempsey would’ve beaten Sullivan to the right cross. It might have come in the first round or the third or the fourth, but the minute that Sullivan tried his, Dempsey would have beaten him to it.” The Washington Times, January 22, 1922.

In another: "We asked Jack who was the greatest fighter he'd ever seen?"

'John L. when he was right. On the nights he was in shape nobody living or dead could have licked him. Not even Dempsey, and he was the second best fighter I ever laid eyes on.'"

Imperial Valley Press, 5 May 1933
https://cdnc.ucr.edu/?a=d&d=IVP1933...xt-txIN-jack+mcauliffe+john+l+sullivan-------

Charles Leahy in 1922;

Jack Dempsey is the greatest Heavyweight that ever lived, or who is living today. Don’t tell me of John L. Sullivan! I saw Sullivan in his prime, and while he was a good one, he could not be considered in the same class with Dempsey?
Sullivan delivered a terrific blow when he landed, but before a good boxer, Sullivan was always like the milkman, 'a little late'.
The Boston Strong Boy beat up the best men of his day, but the best men of his day were a sad lot. Let me tell you, that in the days when Sullivan was ruling the roost and when he was Champion, they'd be able to pick a man off a dray and pit him against Sullivan. Naturally Sullivan would beat all such men. He beat the Pddy Ryan's, the Jake Kilrains, the Joe Gosses, the Maoris, the stevedores of his day and age, but, who among that motley throng, knew the fine art of pugilism as Jack Dempsey knows it?
The only’ man who could fight his way out of a paper bag that Sullivan ever met was Charley Mitchell, of England and weighing fully 40 lbs less than the ferocious Sullivan. They met twice, once in The Garden, in my own state, and later at Chantilly, France. At the first meeting Mitchell struck Sullivan a blow in the mouth that knocked down the great John L. Of course - in what happened after that - Sullivan had the advantage, but show me any man of the weight of Mitchell that could hit Dempsey and knock him down?
ln Chantilly, France, Sully was lucky to fight a draw with the same Mitchell. Now will anyone dispute Dempsey could have licked Mitchell at his very best in a couple of punches - or one punch?
No, I for one, most certainly do not think that Sullivan could hold a candle to Dempsey. Then we will come on to Jim Corbett, who was probably the cleverest of all the first big fellows, but Corbett, while cleverer was not a whit faster than is the Dempsey of today - and the heaviest punch that Corbett ever delivered in his life would fall like a drop of snow on a church steeple on the rugged Dempsey?
Corbett at his very best would have been just about a quarter of an hour's exercise for Dempsey."

 

Is there anyone who sparred both who compared their power or overall ability?