For a rather long time, I was not a fan of classic game emulation. I viewed it as a bastardization of the gaming medium. I also wondered how you could possibly enjoy playing an old NES, or Genesis game on a computer, while not using the original hardware or controllers. Also, having separate emulators to configure, and issues with improperly mapped controls, emulation just couldn't deliver the experience I was looking for.
Fast forward to current day. My views on emulation have turned around thanks to the help of OpenEmu. OpenEmu is a fantastic piece of software that allows you to search, sort, and organize all of your ROMs. The interface reminds me very much of iTunes. It also has the ability to launch the game right where you left off, even if you didn't create a save state. When it comes to the controls, it has a tendency to automatically detect your USB controller, and even properly map the controls for you. I have only tested it with 2 controllers so far (Logitech USB Rumble Pad, and Xbox 360 controller), but I must say that it works fantastically. In OS X I did need to download a driver so that my Xbox 360 controller would be compatible.
http://openemu.org . Feel free to comment, and let me know what games you've been playing.