I've noticed there seem to be a lot of knowledgeable and engaged Magic: The Gathering players around here so maybe you guys can indulge my curiosity -
I played a ton back in the early-mid 90's, basically stopped playing not long after Mirage. I've got a bunch of old cards, clearly most of them are commons/lands/junk. The lions share are Revised/4th edition/Ice Age, with occasional singles from older sets (Dark/Arabian/etc). Maybe a few dozen from newer sets when friends tried to get me back into it by way of a draft evening.
I definitely had a couple "valuable" cards along the way, many of which changed hands long long ago, but a few of which may still be in the mix. The problem is, I actually *played* my cards so none of them are pristine, and some of them are "well played" condition. Clearly these won't hold tip top value, but with the widespread adoption of deck protector sleeves, are people a little more forgiving of condition?
For example, last time I went picking through for nostalgia sake I found one of my Underground Seas. I'm sure I had two of them, I'm betting the other is still tucked into my old Black/Blue Discard and Denial deck (Think Mindstab Thrulls, Abyssal Spectres, and Hymn to Tourach, and Rack/Cursed Rack - all my friends used to hate me).