You've got it, now control it
|Now that you've got your emulators, you need some kind of controller. Sure, you could use a keyboard, but these days that's just too hard. I don't know why but it's hard to get coordinated using the keyboard even though I grew up with keyboard gaming on the Apple ][+. Most USB gamepads and joysticks should "just work" with OSX, no drivers needed.
You can get something called USB Overdrive X which will let you use your gamepad as a sort of keyboard, but it isn't necessary in any of the emulators I went with since they all can use a USB gamepad directly. Also, if you do put on USB Overdrive X, be aware that while it is active it blocks any application from talking to the USB gamepad directly.
Before launching any of the emulators, connect your gamepad to your Mac. SNES9x is probably the easiest to configure, but none of them are really all that hard. In SNES9x go to the Config/Configure Controllers menu. A window will come up with a nice graphical layout of 5 controllers which is arranged similarly to a real SNES controller. Simply click on the button you want to assign, then push the button on your gamepad. It only takes a few seconds to go around and assign all the controls.
For the emulators that use Emulator Enhancer, it's almost as easy. There's no nice GUI layout, but it's still a matter of clicking what you want to change and pushing the button on the gamepad. To set them up, choose Preferences in the emulator's menu, then go to the Joysticks pane. Click the control you want to change, then click the Set button, then push the button on your gamepad. Don't freak out when you see it automatically assign Right when you set Left, or Up when you set Down. It's smart enough to know that if you're using an axis for one direction, you're going to want it for the other direction too. If you're assigning a "hat switch" to a direction, it'll pick up all 4 directions at the same time. Nifty.