I have way too many. I need to sell some. I used to be really good about selling anything I had not played in a couple of years. I'm way overdue for a purge.
Call of Cthulhu
That's what I'm keeping - the rest is going up for sale this winter.
Just going from memory:
Champions 4th Edition
HERO SYSTEM 5th Edition
Star Wars (d20)
Star Wars (FFG)
D&D 5e (Never and mostly likely WILL never see use)
Mutants and Masterminds 3e
DC Heroes (MEGS) 2nd Edition box (Sealed)
DC Heroes (MEGS) 3rd Edition
Marvel Mulitverse Role Playing Game
A few years ago I purged most of my Dungeons and Dragons books from BEMCI up to 4th Edition.
I kept some adventures and books from Advanced and Basic (Like Keep on the Borderlands, Village of Hommlet, TOEE, SCOURGE OF THE SLAVE LORDS, QUEEN OF SPIDERS and the single versions of the modules. Bill Willingham signed my copy of G1-3 so I was definitely keeping THAT.) I got rid of a literal bookcase of 3rd and 3.5 books and adventures and all of my physical Champions books for 4th Edition except for the Core Rulebook which I wanted to get signed by George Perez but never did...