How long will it take? Are there any good tutorials out there?
Try reading this Instructable. Although I would recommend an Emulator installed on an Android or iOS device. You can hook up a PS3 controller to Android with Sixaxis Controller, a $2 app from the Google Play Store. Your choice.
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If you have to ask the question, you wouldn't understand the answer. Basically impossible
It's not very easy at all. You gotta have a good understanding of electronics so you can condense the system as much as possible. Possible moving parts around to accommodate a better portable form factor. Then you need to ingrate the controller and some sort of screen. All the while you need to consider the power consumption of everything and find a suitable portable power source to run it all. But on the bright side all the work has already been done and you can buy a hand held portable NES/SNES game system for $100http://www.thinkgeek.com/product/ed6b/