Not all work but most do(95% maybe). Their are some fun SNES games. I was kinda surprised.
Play around with the bottom settings (like the full screen) for some games. Some require pressing the start button; before you can see them (??).
Personally, the DS games trump all the rest but the rest (snes,GBA) are still fun.
One thing I noticed, why use the older NES emulator when the snes emulator includes games that also cover the older console (like Super Mario Bros III).
The MAME emulator is cool with it's one screen (Pac man, Donkey Kong, Galaga) over the two DS screens but it's really a novelty too. Why? Because you can just play DS Games that cover those classics. Me thinks these are mostly appreciated by us old fogies that actually played Pac Man when they were new; in the arcade! They are not better, just interesting.
Summary: the SNES emulator is the most smooth (after GBA) but don't expect perfection. SNES (and GBA) may give you some more great games but DS is where it's at. It's all a matter of space, isn't it? Can you have too much space?