Using an original game console controller makes a big difference when playing emulated games. The experience can end up being as good as playing an original system. There’s just a certain feel to the buttons that usually can’t be replicated with a newer controller. It’s a combination of several factors (how the buttons feel, the size of the controller, etc).
A couple of months ago I bought some original NES controllers at a pawn shop for about $5 each. They sat in a drawer unused until I purchased two RetroBit Retro Adapter NES Controller to USB Port Adapters (under $12 each) from Amazon.
The adapters seem to work perfectly. I was able to use one adapter and one controller in OS X Lion with Nestopia without any problems. Some time soon I’ll hook up two controllers at the same time to find out if they can be used at the same time for two-player games.
I’ve very satisfied with these adapters. Playing older games with them is a lot more fun that using a modern USB controller. I’m looking forward to receiving a set of SNES controllers I’ve ordered, which I’ll use with an SNES to USB controller adapter that I already own.