Reading through the thread, I'd like everyone to know that Picodrive core for Retroarch (.CIA) runs Genesis games nearly flawlessly, and Sega CD with required bios runs 80-90%, running Flashback CD, will try Lunar 2 soon. FMV runs about half-speed, so wouldn't be good for FMV CD games. CD music doesn't seem to affect framerate, but vocal samples do, probably processes differently?
Every Genesis game I've tried runs at or close to 100%. I tried a romhack of Sonic 1, S Factor: Sonia and Silver, and it starts running okay, but crashes the entire system when it gets to the title screen. This doesn't happen on GenesisPlus core, which runs the game at around 30% speed.
I've yet to find a decent SNES emulator.
Emulators I'm using that are close to 100%:
QuickNES, GameYOB, Picodrive, CIA injection for GBA (gpSP about 10-12fps, mGBA crashed loading the ROM)
blargSNES 1.2 runs a few games. DKC 1 works, but not 2 or 3. No games which require external processors or Mode7 (such as F-Zero) work either.