Very interesting! Andre Weissflog aka floooh is very much one to watch: great to see both development out in the open, and clear explanations of what’s happening and why. To get pixel-perfect games, demos, and software protection routines, you need surprisingly intricate emulation of all the complex chips in a system.
Andre has a showcase of 8 bit emulators here, to run in your browser:
(Robotron, Commodore, Sinclair, Acorn, Amstrad)
In the same vein, Matt Godbolt has written up some of his adventures in writing JSBeeb, and has also got a couple of talks up online: