Mega Game Controller

I have a ton of programming experience. I'm trying to hook up arcade joysticks and buttons to the Arduino. I know how to hook it all up. The problem I'm facing is how to get the signal from the Arduino to the game program.

Can I use the existing USB port it comes with? Do I have to write a driver for the Arduino to communicate with the game emulators? (Nestopia, ZSNES, stuff like that) How do I write a driver? lol Is Firmata, or something like that, what I want?

I have seen someone use a Bluetooth shield to do it all for you, but I want to do it as simple as possible without having to buy anything else.

I have looked and looked, and don't know where to find the answer.