There was Slayer, then they later released Death Keep. I think if you get that chance to play them that you'll find your self liking Death Keep the best between the two.
I also really enjoyed playing Alone in the Dark part 1 on there, as I believe this was the only console that that game ever made it to, which was ironic as that games still stands (in my opinion) as the best in the series.
I believe it was the 3DO port of Flashback that featured the hi-resolution graphics which didn't grace the PC till much later. And of course there were a few RPG's on the 3DO that I loved playing, though I forget the name of the one I played the most...
Speaking of which did anyone ever get a chance to play Lost Eden? Was it any good?