Spinks beat a fat, old Holmes! Means nothing! Thats like saying Johnson beat Roy, and Bernard beat Johnson, so BHOP is greater than Roy.....even though we know Roy schooled BHOP. Doesnt mean anything, a Prime BHOP was the one around the time he fought Tito, a Prime Roy was the one who fought at super-middle, and a Prime Johnson is NOW!
As for the matchups, MAN, the two Sugars vs eachother would be the best I could think of, and I would take Ray Robinson any day of the week, probably by decision, after putting Leonard down a couple of times! Especially Ray Robinson over the 15 rounds. These are the two greatest fighters of all-time IMHO.
As for some of the other fights mentioned:
A PRIME Tua (the one that fought Ibeabuchi), not the lazy plodding Tua, could give Foreman a tough time, but I would take Foreman by decision.
Tyson V Frazier, Tyson KO3
Marciano V Holmes, Holmes by close decision. Boxing just changed too much over that time, and Holmes Jab, movement and speed would be too much for the slow Marciano.
Ali V Lewis, Ali. Lewis, even in his big fights, did not look spectacular. He looked slow and had a low output when disposing of a past it Holy. His main attribute is his KO power, but then again, Ali would take his best on the chin, any day of the week. Ali by decision.
Vitali Klitschko VS Lennox Lewis II, Lewis is old and would be ruined now in a rematch, Klit KO5
(prime-to-be) Miguel Cotto VS Roberto Duran, lol, Duran and Cotto are in a different universe when it comes to boxing, Duran KO5 or decision.
Miguel Cotto VS Tito Trinidad --at 147lbs, Tito KO8
Jake LaMotta VS Bernard Hopkins, man, could be damn close, LaMotta in his face all night, much as Echols was, but LaMotta would remain there for 15 rounds. The fight would be very very close, as BHOP has a granite chin and had a HUGE punch-output in his prime, too close to call.
Cassius Clay vs Joe Louis, another fight nearly too close to call. I will say Clay by CLOSE CLOSE CLOSE decision. Both were the most complete heavyweight fighters ever to grace the sport.
All these fights are assuming the fighters mentioned are in their PRIME.
Some of my own dream matchups:
Roldan V Echols
DLH (lightweight) V Henry Armstrong
Mayweather Jr, V Saddler or Pep
DLH (light-welter), v Tszyu or Pryor
Hearns (welter), V Robinson
Hagler V Monzon
I have hundreds more, but I will just leave it at that.