The Blissbox 4Play is a device that allows you to connect old video game controllers to modern devices via USB. It can accept 4 controllers at once and does so using patch cables that adapt your existing controller to the 4Play.
It doesn't require you to install any drivers on your machine, works with rumble, Dreamcast VMU, microphone input, you name it. It's both the best and most cost effective device I've found for these tasks.
Recently they put up a kickstarter to produce a new set of cables that includes more obscure connections than their original set.
I'd encourage anyone looking for a great emulator controller solution to research it themselves and back their kickstarter if it's something that you're interested inhttp://kck.st/1WtOevm