Another great SNES emulator for OS X
ZSNES is a well-backed, cross-platform SNES emulator, and this page will help you find and install it!
Download & installation instructions
The current Mac version of ZSNES can be found in a thread in the ZSNES forums.
The file is called ZSNES 1.51-3.dmg or
Extract ZSNES.app, move it to your Applications folder, and you're ready to play SNES games on your Mac!