[Robextend]

I would think the 1989 Upper Deck Factory Set along with variations would be a good read. I agree with the 1990 Leaf and 1992 Bowman sets as well.

I also agree with Jeff that any player who places with the greats in the history of the game would have pretty good value:

Pujols, Griffey Jr., Jeter, Maddux, Johnson, Rivera, etc...