I will take Ice Colds list as I am lazy:-

Joe Calzaghe vs Sven Ottke would be easy win for Joe who would beat him with on hand tied behind his back.
Juan Manuel Marquez vs Naseem Hamed - JMM would have beat him which is why Naz avoided the fight.
Razor Ruddock vs Evander Holyfield would have been a classic, with Holyfield winning.
Michael Spinks vs Marvin Hagler, damn difficult, Spinks on points
Earnie Shavers vs George Foreman, KO by Foreman

Mines would be :-

McCallum v Fab4 he beats Leonard and Duran at LM, looses to Hearns and Haglet at middleweight and

Herol Graham beating Eubanks and Watson points and stopping Benn in10.