Make:

NES.app is a full blown Nintendo emulator for the iPhone. It supports the device's multitouch interface, so you can use the virtual on-screen game pad with your thumbs, just like the Nintendo gods intended.

NES.app uses a heavily modified version of the InfoNES emulation core to mimic the 6502 processor in a Nintendo Entertainment System, allowing you to play ROM dumps of games designed for the NES console.

NES.app started as a fork of iPhoneNES v0.01, but has been completely rewritten to run very fast, and with many additional features including sound, multitouch support, full-screen, landscape mode, game genie codes, saved games and much more.

It's supposed to run pretty well, but if you're using game genie codes or a more graphically demanding title, there's a frame-drop feature... It'll still play realtime, but just a bit choppier.

What I'm really excited about, though, is the state saving ability, which allows you to stop a game mid-play and then start it again from that point at a later time. I could never beat Contra even after resorting to some "up, up, down, down, left, right, left, right, b, a, b, a, select, start" business, and my Super Mario skills have always been wanting, so maybe this is my chance to regain some 1980s self respect.

NES.app: The Nintendo Emulator for iPhone - Link