My most valuable cards from the 1990s are definitely insert cards. I had some good Emmitt Smith insert cards that at the time were going for 50-75 bucks. No idea what they are now. From my uncle's cards, I have a Ricky Henderson rookie card (1980 topps), Andre Dawson rookie (I think 1976 topps), and Ozzie Smith rookie (1979 topps?). The cards were in surprisingly good condition, but no idea whether they would grade out to mint or near-mint by all the psychos who grade these things with an electron microscope.