Make sure you’re fully up to date (as this affects the performance of a few emulators).
My list of tested emulators:
Gb (libretro) – 100%
GBC (libretro) – 100%
GBA (GPSP) – 100%, barring some titles with hacker’s title screens added
GBA (GPSP-libretro) – 100%, barring some titles with hacker’s title screens added
Genesis (libretro) – 100%
NES (libretro) – 100%
SNES (libretro) – 100% (on Rpi2 this includes SuperFX titles like Star Fox as well!)
N64 (libretro) – 40%, some titles perfect, most titles laggy, some fail to start
PSX (libretro) – 100% (with correct settings)
MAME (libretro) – 100%, but you have to use the correct games to match your BIOS which is always an issue with MAME
Doom (libretro) – 100%
Quake III – 100%