I suffer from a severe case of collectoritis. I don't sell or trade in anything. I even keep games I hated...
Way back in the day when I was much younger and strapped for cash I sold some of my Super Nintendo games (some really good ones, like Final Fantasy III and Legend of Zelda: A Link to the Past) and I have never forgiven myself. Seriously, it haunts me to this day.
Oh hell yes, I am the same exact way, with a similar backstory. Instead of SNES titles, I sold a few old gameboy games and GBA ones... all for just some freaking trading cards (which wind up later getting stolen) and I too never forgave myself, and felt like a traitor. Heck, even if the game is blah, if it is cheap, I still get it anyhow, and build up the ever-growing collection, and just feel good on having all this stuff, even if my backlog is impossible to finish.
The pic below is a partial example of how obsessively big the gaming collection is coming, and it still grows.http://img.photobucket.com/albums/v616/Chimizard/DSC00511.jpg