I am keeping the standard A500 and A1200 in mind, when saying "This could be done", and not modern PPC machines
Street Fighter Alpha and Street Fighter Alpha 2. Could be easily done. (I think all Street Fighters on Amiga could be done better. Haven't seen SSF turbo, though)
NBA Jam... the 1 button joystick would be a problem, but besides that, could be easily done.
Power Spikes - A good volleyball game from arcades, also on the Mega-Drive and the SNES. An Amiga port would kick ass..
More arcade shmups, like: Truxton 1 & 2 , Dogyuun, Batsugun... I believe they all could be easily done (Batsugun would be great on AGA machines).
More fight games: Most Neo-Geo BEUs could be done. Art of Fighting, Fatal Fury, World Heroes (It sux, but I would like to see it on Amiga anyway), and the KoF series.. (Athoulgh the KoF series would need to be for the CD32.. imagine the amount of disks would be needed to put KOF
Games from Treasure.. they probably doesn't even know what an Amiga is, as they are from Japan, but hell, they could squeeze the most incredible code in the 68000 ... check out their Mega-Drive games. (I love Alien Soldier's phrase in the title screen: Visual Shock, Speed Shock Sound Shock, now the 68000 heart is on fire)
A decent port of Power Drift. Anywany, that would be asking too much, I haven't see one single decent port of it.
Damn, too many already