yes, i just tested with a few additional snes and genesis games, they are running perfectly, however i did have to manually add that info in the command line argument to get them to launch. Also i am using the My Arcade Wireless controller for NES Classic. All of the front buttons were working except i wasn't able to get L and R triggers to work. I am thinking its probably because this controller actually has two left triggers and two right triggers, which is probably different than retroarch is configured for currently. I'm not quite sure how to find the retroarch controller settings and get the triggers working at the moment. I tested with street fighter 2 on snes and mk3 on genesis for a 6 button layout. The 4 front buttons x,y,a,b worked great, but the L and R triggers did not work, and i could not figure out how to assign them in retroarch.
In an unrelated note, I'm not sure why Sega master system games are pointed to a different emulator than genesis gx? i thought it could run master system, genesis and game gear? Is the standalone sms core a better emulator option?