There'd have to be an onboard-emulator as well as a bios to run the whole thing?! I think that'd be really a hard piece of work.
http://www.retrousb.com Get the PowerPAK to emulate just about any mapper and load any ROM. The NES on a Chip clones suck ass. Sound is wrong. You won't notice it in every game, but the duty cycle is fucked up. SMB1 I believe was pretty horrible sounding. Also few are wired up to work correctly with mappers like MMC5 I believe. That means no Castlevania 3. If you want portable NES, get a PSP and emulate. If you want to play NES at home, get a NES. Don't settle for pirate trash. Sure they are cheap and interesting to fuck with. But when you go to do some gaming do you really want to do that on a piece of shit or would you rather a quality system that behaves as intended?