Jimmy Young was one of the very underrated fighters who fought during the golden era of Heavyweight boxing. He beat Ron Lyle, Jose Roman, and George Foreman. He also had close decision losses against Muhammad Ali and Ken Norton as you said.
But I believe if Ali and Norton rematched him, they would have dominated. And Foreman would have knocked him out in a rematch in my opinion. Earnie Shavers and later Gerry Cooney stopped Young, and Rocky Marciano, who makes better use of his power than Cooney or Shavers, would dominate in my opinion. Plus Marciano would use his very underrated defense and head movement to get inside easier. In about the fifth round, Marciano stops Young.
Marciano TKO5.
You're right, I've always had the opinion that Jimmy got the screws in both the Ali and Norton bouts as far as the Foreman fight no much can be said, Jimmy clearly won that fight. Jimmy could box a true Gladiator from the gyms of Philadelphia.
There's a fight in which Jimmy fought and got Knocked out in and that was a bout against Ernie Shavers and although Jimmy fought "Up" to the abilities of his opponents, I'm of the opinion that if Shavers could stop Young than Marciano wouldn't have any trouble stopping him either.
The thing about "The Rock" was he could punch just as hard in the last round of a fight just as he did in the first round of a fight. Rocky's short all angle punches would be a little bit too much for the forever willing to trade Young.
Marciano stops Young before the seventh round.
Ali was already on decline and overweight in that fight hence it should not be a gauge of Young's worthiness as a fighter. What more, Young often intentionally put his head and upper body out of the ropes to avoid Ali's inside attack on the ropes and the corners and prompt the referee to separate them.It was smart but cowardly. He never hurt Ali in that fight though he landed many punches, most powder puff anyway intent at winning points which obviously did not sway the judges.
The same could also be said of his fight versus Norton although he really won over Foreman.
What is clear was that Young lacked the punching power and the guts and most importantly, the consistency in his performance.
That would have been fatal against a powerful, steady tough champion as Marciano.
Marciano by KO within 10.
Jimmy Young has the size, power and the right skills set to beat Rocky. Unfortunately, he ain't tough and smart enough to be able to get it done against a strong, tough and hard-hitting slugger like Rocky who just let it all hang out every single round.
Rocky
this would go just like Holmes vs Cooney, or Johnson vs Burns, or Tyson vs Savarese
There are those who say that Young beat Ali and Norton. He beat Foreman. He is arguably 3-0 against 3 hall of famers