Here are the games I have played so far.
The Need for Speed-(of course

Wolfenstein 3D- (best version i've played imo, I would have never thought I would be playing and enjoying Wolf 3D again, but the 3DO version is just awesome)
Gex -(haven't gotten too far into it, but it is a great platformer)
Lemmings -(very good version, excellent music and a Fast Forward button so you don't have to wait on those slow Lemmings)
Sewer Shark- (if you are into that kind of game. I am


Doom- Could have been the best console port of Doom. Excellent music but a TERRIBLE framerate, not to mention that to enable full screen you have to enable a cheat code, people say that decreasing the screen size speeds up the framerate but whats the point? I'm not playing it in a postage stamp sized window.
Road Rash- seems like a decent game, haven't really played it much
Crash N Burn - Seems like a nice racing combat game but my 3DO has trouble reading the disc which causes a couple second freeze up every now and then so I haven't played it much.
Microcosm- Only played it for a few minutes, didn't seem that great to me.
I'm wanting to try one of the RPGs the system has the one I seen looked pretty decent.