I guess I'm one of the few people that never let go of any games or consoles I've ever owned, from my Atari on. Call it sentimental, call it collecting or call it just being a pack rat but I still have them all.
Obviously, I've never traded in any games. When it comes to buying games, I do buy all my games brand new. There is something that bothers me about buying a used game but I have no problem renting games. Over my lifetime, I've rented way more games than I own.
My current Playstation library (PS1, PS2, PSP) is somewhere around 60 games.