While the NES Classic Edition is built in mind for Retro games from the NES Era, that doesn’t mean the device is a weak system. In fact, the system is more powerful than Nintendo’s Wii & current generation handheld the Nintendo 3DS.
Smarter people have looked at the NES Classic Edition innards and deciphered just what’s tucked away inside the system. Believe it or not, most of these specs are above what is offered in the Wii and 3DS.
SoC: Allwinner R16 (4x Cortex A7, Mali400MP2 GPU)
RAM: Hynix (256MB DDR3)
Flash: Spansion 512MB NAND
Speculation on my Part with no sources of fact backing this up: This could mean that similar hardward to the NES Classic Edition could be utlized for a possible SNES Classic or Nintendo 64 Classic systems.
Sources: Go Nintendo, NeoGaf, Reddit