I do tend to hoard, out of nostalgia, but recently I've found that nearly three decades of collecting games has meant that I need to be selective about the games I keep.
It's not so much the really old games; I have Spectrum and Amiga game boxes which I love and cherish like museum pieces. The ones that cause the most problem for me are PS1, PS2 and DS games.
They're not generally old enough to have real collectable value yet, either. I often think if I'm only going to get 50p or £1 for selling them on I may as well keep hold of them. If I do trade them it's usually just to make space.
I've held on to many of them in the belief that I will replay them at some point, but realistically I have as-yet-unplayed games on my shelf, so when are old titles going to get a second look?
Having said that I did dig Vib Ribbon out for the first time in about 7 years. It's still mad and great!