For performance, out of 10 (Sound/Framerate/Compat/Overall):
Snesemu: 0/7/6/5
SNES9XGP: 9/4/9/5 (haven't tried the latest ver)
SMS32: 8/10/9/9
InfoNES: 4/5/5/5
fNES32: 0/5/4/4
FrodoGP: 8/10/8/9
GPengine: 8/8/8/8
PlusIVe: 9/9/9/9
WonderBoi: 0/9/6/7
GPSpeccy: 6/10/7/8
I was fairly generous with these scores. Basically, if all you want is Nintendo stuff, it's not going to satisfy (which is kinda ironic, really). Of course, most of these emus are still under development and will probably improve over time! (FYI I wouldn't give an emulator 10/10 unless if it had everything the original machine did and no compatability problems, except on maybe rare occasions - eg, on pc, CCS64 and ZSNES I would probably give a 10)
Individually though...InfoNES has really bad sound, and like MrT said, so did the PC version. The GP32's is even worse. Neither it or fNES32 run very well (both are ports of InfoNES on PC) and have poor compatibility - eg, SMB3 runs really slow (does it run in fNES32?) and Punch Out runs REALLY slow (it doesn't run at all in fNES32) and you can't play it, really. Especially since it has graphic glitches. A few games are playable decently - eg Megaman, but anything with a bit of speed (SMB1 even) is probably a big no-no for now. Give it time. It can only improve!