Mayorga vs Vargas was pretty good fight although both fighters were washed up, especially Vargas. Lewis vs Tyson, Floyd vs Manny and RJJ vs Trininad all were bad fights
Holyfield - Tyson Leonard - Hearns (talked about in 1979) Hagler - Hearns (originally scheduled in 1982, before Hearns broke a finger) Holmes - Cooney (postponed from March 1982)
In Four Kings, If you believe Dundee (oh Angelo, I am sure you were working us), he stated the fight was signed to happen in late 78, while he (Dundee) was on holiday. When he got back Dundee cancelled the fight straight away!
Carlos Palomino v Armando Muniz - postponed twice in '76 before taking place in early '77 - a great fight. Mando Ramos v Chango Carmona - was to take place in '69 and '71 before finally taking place in September of '72 when Mando was well-worn. IMO would have been memorable had it taken place on any of the earlier dates, but Chango ripped him up pretty bad so don't know if this counts. Jeff Fenech v Azumah Nelson III - OK, I cheated. I don't know if it was a good fight or not as I've never seen it. I don't know what we got since it was 16 years after their 2nd fight.
I was going by memory, seeing it discussed on a TV broadcast of either a Leonard or Hearns bout. I didn't realize it had been signed (like you said, if you believe Dundee). This is a fight that got better, or at least attracted FAR more mainstream attention, because it was held later when they both had belts.