Pick a fighter whos's best performance was in a exciting fight?

Mercer (Mercer's peak) Vs. Lewis

 

Riddick Bowe against Evander Holyfield (1st fight)

 

In terms of best performance, it depends on your preference and Hagler certainly had many great performances to choose from.

I consider his best win to be Hearns, which is a reasonable candidate for his best performance too and was most certainly an exciting fight.

 

Bowe in his first fight with Holyfield. It's the best Bowe ever looked, and it was a damn good fight.

 

Brandon Rios beating Mike Alvarado in the 1st fight.

 

Maidana beating Broner.

 

Duran beating Leonard in Montreal
Frazier against Ali in FOTC
Bowe Vs Holyfield

I would venture to say that with ATGs, most of their best performances tend to come against non-ATG opponents, where they showcase their skills to an excellent degree.

 

Leonard against Hearns in their first fight.

 

Unpopular opinion: Ali had one of his best career performances in FOTC even in a losing effort.

 

Michael Carbajal vs. Chiquita Gonzalez
Vitali vs. Lewis
Marquez vs. Pacquiao 4
Shane Mosley vs. Oscar De La Hoya 1
Cotto vs. Shane Mosley

Paul Williams vs. Sergio Martinez 1
Any Michael Katsidis or Bobby Chacon fight

Kendall Holt vs. Ricardo Torres
Ricardo Torres (losing effort) vs. Cotto

 

When Hearns was beating him until he got tired ?!

 

Salvador Sanchez against Wilfredo Gomez.

 

FOTC (Joe Frazier)
Brawl in Montreal (Roberto Duran)

 

I thought Ali's performance in the FOTC was extraordinary! After being out of the sport for 3 and 1/2 years he had only 1 and 1/4 tuneup fights (the Quarry fight was only 3 rounds) to prepare for an all-time top-10 HW at his career peak. In many ways it was his finest hour!!