I did a little bit of testing with basic cores, these are the ones that I use. Not extensive/OCD test, just enough to play a little bit without too much stress.
MAME: mame2000 - Emulation is not very accurate but at least most of the games that I use seem to run pretty well.
NES: quicknes - Everything seems perfect with this core. I have not tried FCEUmm, maybe someone can post a comparison.
Atari 2600: stella - it runs perfectly.
Game Boy / Game Boy Color: gambatte - it’s alright, just remember to put the BIOS in the retroarch system folder, otherwise it does not work properly.
Game Boy Advance: stock MGBA version - runs well but most challenging games have slowdowns (for example GT Advance 3, if you want a benchmark).
Neo Geo: fbalpha - for some reasons I could not get the FBA 2012 versions to work, anyway this version runs fine (except for Neo Turf Master, maybe I have a corrupt rom, I have to double check that).
Playstation: stock Pcsx runs fine with Frameskip, but it has slight problem with hardware pushers like Tekken 3 and Wipeout XL
For SNES: snes9x_2005 - again, there are problems with games such as Star Fox
Most emulators runs fine, there are problems with some games that are notoriously difficult to emulate (like Star Fox on the SNES or Tekken 3 on Playstation). This is because we are forced to use older cores to make most of the games playable. When I say “playable”, I mean without sound stuttering, that it’s not acceptable in 2019. I think the hardware is capable to all this games up to Playstation 1, it only need the right software to do it.
Has anyone been able to get Vectrex to emulate on the GameShell? I just get a blank screen them goes back to menu. Perhaps I am missing something? Thank you.