Here are some links to some "Closet Classics" stories from MaxBoxing on fights that might not have been the biggest at the time, but turned out to be classics nonetheless.
Somebody may get on my case about posting these, but to me, these are great reads.

Junior Jones vs. Paul Ingle (I remember seeing Junior Jones on Tuesday Night Fights on USA)

http://www.maxboxing.com/Groves/Groves112608.asp

Kevin Lueshing vs. Chris Saunders II

http://www.maxboxing.com/Groves/Groves111808.asp

Kastuya Onizuka vs. Thanomsak Sithbaobay II

http://www.maxboxing.com/Groves/Groves110408.asp

Gene Fullmer vs Carmen Basilio I. I guess not closet since it was FOTY, but no one talks about it. That fight was ****ing fantastic.

I forget which fight, but there is also this japanese fight from 1997 that was also incredible. I wish I remember the fighters names. I know they were small, I think 112 or 115.

A lot of those lighter-weight title fights are just flat-out wars that should've gotten tons more publicity than they did.