Nestopia is the one of the only cycle accurate emulators for the Nintendo Entertainment System (NES). Thanks to its highly optimized cycle accurate nature it allows the emulator to have an almost 100% compatibility.
Thanks to the emulator being heavily optimized and the NES system not being overly complicated, the cycle accurate coding does not come at a significant performance requirement like newer systems such as the Nintendo 64 or even the SNES.
Nestopia also has support for all major operating system, Windows, Macintosh and Linux making it one of the more versatile of emulators. If your not bound by a very low powered CPU, one with less than 600MHz this emulator is your best option for playing NES games.
Sadly Nestopia is no longer in active development with the original programming team officially ending its development in 2008, however their have been multiple forks off the base code.