Bible Adventures and warfare are deifnitly the two most common with joshuah and King of Kings a close second. I found Buffet and sunday funday once in the wild on seperate occasions, those titles are worth picking up new because the quiz books and such are very hard to find, I think it's a good investment to pick up those last 2 titles new from Wisdom Tree, or cheaper on e-bay (as I did)
As far as genesis goes, the Wisdom Tree games are pretty rare for the Genesis, I'm probably going to order Joshua from them because I can't seem to find the Box and instructions for that title everywhere, I found all the others at a descent price complete or sealed