All my old games were given away along with the system to younger relatives. The oldest games in my collection now are GameCube ones, as well as Leaf Green. Don't have anything older than that.
Now, if I did have my old games still, it would honestly depend on how much I liked playing them or whether I could make a killing on selling them. Nostalgia goes by the wayside when I can get $500 for something I paid $30 or $40 when it first came out - unless I really, really enjoyed said "collector's item" game.
I am known to sell games that I didn't enjoy playing.