@plwiatt The Pi detects player 1 as joystick 0 and player 2 as joystick 1. Have you tried just plugging into the other port of the adapter? From what you're saying, it looks like you've got the ports mixed up and are plugged into the player 2 port.
@dipkid Poor SNES, now it’s just a boring emulation box with input lag and no cart support. I always wonder what people do with the original OEM board. I assume they throw it in the trash since they never mention anything about it.
The 'Generic 104-key PC' would likely be the best model setting. Also, the keyboard layout settings are all set to UK by default, so if you need anything else, select 'Other'. It appears as though the Rii i8 has an AltGr key on the right, so 'Right Alt (AltGr)' is applicable to you as well.
Ok, that gave me pointer to look for what x86 packages I had on the system, looks like mesa-utils as from www.deb-multimedia.org was causing all the problem.
Removed the foolishly incorrect repo, RetroPie-Setup --> Install Kodi worked perfectly.