I was deep into Pokemon cards in high school (wassup, Karl?!) and even won two badges in a local league before Yu-Gi-Oh took over.
After realizing that Pokemon cards take up a lot of space, I threw them all out except for the foil cards and one of each other card, then put 'em all in a binder. I look through it from time to time and reminice, then wince when I consider how much money I blew on Pokemon cards.
(and still do--I look through the random cards in comic shops to this day, looking for the few foils I still desire*)
*Like Shining Celebi, who is not worth $25, Bosco's.