x68 is very cool. hunt around and you can find an emu for your PC
(the one i've got is in japanese.. it's a bitch to set up, but not THAT difficult. of course you've all figured out how to get a GP32 running, so I'll just shut my mouth right now!!)
lots of the "usual" games, arcade perfect ports -- afterburner, rtype, space harrier, ghouls n ghosts, etc. better gfx then sega genesis, not as good as snes.
this would be a GREAT emu on GP32 if someone could whip it out, i'd say unlikely as it's one of the more obscure systems but.. who knows!!
(note: a very cool version of castlevania came out for this system, rereleased for PSone as "castlevania chronicles" a couple years back..)