I think the CDI could make for a fun night with some friends, y'know, to laugh over the terrible games.  The only experience I have with it though really is playing it for a couple minutes back when it was in stores, that Zelda game was on demo.  Many of the others I've just watched a youtube vid on.  If there are any good games for it, I don't know what they are!
As for the 3DO, I actually picked up years back so I could get the 3DO version of Policenauts and Policenauts Pilot Disc.  I don't really have anything else for it but I think there's some potential in the library if you like that era of early CD-Rom/FMV laden PC titles.  I do, personally, just never really picked any up (yet).  I think I also remember it being known for one of the best Street Fighter conversions at the time, too, but don't quote me on that.  i can't even say which one for sure - II Turbo I think?  When they added Cammy.