Try Higan (Formerly BSNES) for SNES. It claims to be 100% accurate emulation for SNES. What I hear is the guy who made the emulator also personally imaged every snes game that has an extension chip and reverse engineered to to make sure the emulation is perfect and cycle-accurate. It also emulates other nintendo systems, and I have used it for NES with good results.
Otherwise, if you want fast and hacky, zsnes is great for snes on slow systems.