Item — HN Reader

I think if you're new to emulation it's generally a good idea to start with something even simpler - the chip-8 system

http://www.emulator101.com/introduction-to-chip-8.html

An average programmer can probably get an emulator for that running in a weekend, and there are lots of guides and documetnation out there for the opcodes and similar.

NES / Gameboy / GameGear / similar are probably well-documented, but they will be harder at least because the processors have more opcodes you have to care about.

Yeah CHIP8 is a simple enough system that i even made two emulators (one in DOS and one in Windows) and an assembler back in 1999-2000 or so when i was in highschool and could barely put eight bits together to form a byte.

Also somehow for some reason i was convinced back then that mobile phones in the future will have a CHIP8 emulator to play games :-P. Sadly(?) they got Java instead.