BSNES/Higan is the most accurate, althought it requires a powerful machine to run fullspeed.
SNES9X is a very good emulator. Very accurate and runs every games almost perfectly, and it doesn't require a super computer to run. This one is recommended for everyday use.
ZSNES/SNES9X 1.43/SNESGT are quite obsolete, or less accurate, but they remain used, mostly for older ROMhacks, especially when console verified content doesn't work well on better emulators. I personally like SNESGT in this case, it provides excellent emulation, and most of the stuff I ran on it worked perfectly.