Salvador Sanchez and Eusebio Pedroza won the WBC and WBA featherweight titles in 1980 and 1978 respectively. They fought and beat almost the same sets of challengers at the height of their reign but they never got to face each other and there never were plans to pit them despite media and fan demands up to the time Sanchez died in a car accident late 1982.

There's a window of opportunity also for the likes of comebacking George Foreman and Mike Tyson to fight from late 80s through the mid to late 90s, KO artists David Tua and Tommy Morrison in the mid to late 90s

Brian Mitchells, Hector Camacho and Julio Cesar Chavez never got to fight among themselves at 130 lbs. despite the trio reigning over the division for most of the 80s.

Scared Tyson vs Foreman and Lewis (earlier).

The Klitschko's ducked James Toney, in early 2000's.

Everyone ducked Lennox Lewis , in the early 90's

Bowe , Tyson, and Foreman, Tua would of all been great facing each other

Old Holyfield vs Whlad

Whlad vs Valuev just for the entertainment

Young Floyd vs Barrerra, Morales, Prince

Hopkins- Toney

Sven Ottke and Calzaghe

Sven Otke and anyone outside Germany where he got all the decisions

lewis vs bowe should of happened but never did

going back a bit further azumah nelson vs barry mcguigan

duran vs pryor........

Obviously there are various reasons for boxers to never be able to make a fight but fights like Bowe vs Tyson, Eubank/Benn/Collins vs Jones Jr/Toney, Mayweather vs Pac etc could have been good fights.