reading through neo geo documentation and absolutely salivating. the specs are very close to the mega drive, but you can do so much more with the graphics and sound...
i'm actually tempted to look into the possibility of converting sonic 1's source to work with it. it seems that most of the effort would go toward converting all the graphics to use 16x16 tiles instead of 8x8, as well as reorganizing the ram usage so that the game doesn't trip on the ram reserved by the system rom... there's a few other changes that'd have to be made as well, but thankfully the code keeps most of its interfacing with other parts of the hardware within a single area of execution (the v/h interrupts)
ooooh this sounds interesting! The only thing I know about the NeoGeo (which may or may not be correct?) is that it only does sprites, so could you please link the docs so I can see what that beast of a platform can do?