A few bullet points here:
- Neo Geo is considered by most to be 24-bit end of story
The Neo Geo was marketed as 24-bit; its CPU is technically a parallel processing 16/32-bit 68000-based system with an 8/16-bit Z80 coprocessor, while its GPU chipset has a 24-bit graphics data bus.
- Putting arcade games in the challenge will create unecessary questions and fuss. I can already see people asking "is this 16 bit"?
- Limiting this to the consoles in the rules list makes the challenge more focused
- Concerning fighting games, if you feel satisfaction including them in your list, go for it. This challenge is for you to enjoy.
Again, the whole point of the challenge is to beat some games you've never finished or revisit some old favorites. The challenge is all what you make of it but we do need to keep some guidelines. If you want to do an arcade challenge, go ahead and make a new thread.