http://www.technobuffalo.com/2016/11/04/nes-classic-more-pow...
It was only relatively recently that you could run a high-fidelity (bit-perfect, cycle-by-cycle actual emulation of the underlying hardware) emulator of an N64 on a PC. E.g. Project64 required a Pentium 4 with 1GB RAM and a GeForce 9000 in order to emulate a 94MHz R4300i and its vector coprocessor. (And I'm not sure how many shortcuts Project64 takes.)
Anyway, it might be that the hardware is overkill because they want to use it for other platforms, or it could just be that they're doing very high-fidelity emulation and are just beating the performance problems into submission with transistors.
Super Metroid
Super Mario 1
Super Mario 2
Super Mario 3
Super Mario RPG
Super Mario World
Legend of Zelda: A Link to the Past
Legend of Zelda: Ocarina of Time
Sonic 3
Kirby's Dreamland 3You can't beat the feel of a genuine, 20 year old controller!
They also make them for pretty much every controller you could want - Even Wiiport to USB which means you could plug these NES Classic controllers into the PC to use with emulators directly.
I wish these all worked with Steam Link though :(
Every supplier in my area has sold out multiple times already.