Also, how many open source emulators haven’t been ported yet? Are any of these any better than the ones already in the list of cores?
One that i can think of right now is Project 64. This emulator has been open source for a while now but it seems like nobody cares about it being in RetroArch. I believe this emulator is superior than Mupen in almost every way. I have been testing the standalones for years now and i don’t remember a single game that runs on Mupen and can’t run on Pj64 (especially the latest version) but i can think of a few games that don’t even boot in Mupen and play very well on Pj64 (World Driver Championship and Stunt Racer 64 being the ones i care the most).
Other than that i can’t think of anything else though, except maybe the atari800 emulator that just got a very nice core for Atari 5200 support (although still not in the online updater).