I've been collecting for 3DO for several years now but I only know of a few games that are actually rare and go for alot of money(Lucienne's Quest being the main one). What I would suggest is to pick the games you like or are interested in and if you feel their price is too high go for the Japanese import versions. 99% of them will play on any 3DO system and many are English friendly as well. But most importantly they are usually much cheaper than their US counterparts.