Sorry, I should have clarified: The Game Boy is very simple in concept and on a sufficiently high level. But this is exactly what allows you to get payoff quickly, and why I like it for educational and experimental projects. Especially earlier games like Tetris don't significantly rely on many edge cases and implementation details, so even a quick and dirty implementation runs them reasonably well.
Once you want to do "serious" emulation that runs a wide variety of games and accurately reproduces them in every spect, things become much less simple and might also lead you to completely abandon initial approaches, e.g. because your straightforward but non-cycle accurate CPU main loop doesn't cut it anymore.
Compare this however with a more modern system that has an MMU, where you have a long, long road of busywork ahead before you can even get past any reasonable definition of "booting", whereas for the Game Boy even a shoddy first draft implementation might at least get you into a game's initial menu screen, completely with working buttons and all.
And strictly spoken, a conceptually more complex system will have more edge cases and implementation details to deal with, albeit I think that it often also means that those implementation details are less exploited, as developers stay on a higher level and are less trying to squeeze out every last bit of the "simplistic" hardware.
And the simple front with the fractal complexity below it also make this more fun and educational: You can start off easy while still getting good results, and go arbitrarily deep in perfecting your emulator, choosing from an apparently still unexhausted variety of interesting problems to solve.
Your links are a good example, I love reading about the complex implementation details in emulators of superficially simple hardware.
Once you want to do "serious" emulation that runs a wide variety of games and accurately reproduces them in every spect, things become much less simple and might also lead you to completely abandon initial approaches, e.g. because your straightforward but non-cycle accurate CPU main loop doesn't cut it anymore.
Compare this however with a more modern system that has an MMU, where you have a long, long road of busywork ahead before you can even get past any reasonable definition of "booting", whereas for the Game Boy even a shoddy first draft implementation might at least get you into a game's initial menu screen, completely with working buttons and all.
And strictly spoken, a conceptually more complex system will have more edge cases and implementation details to deal with, albeit I think that it often also means that those implementation details are less exploited, as developers stay on a higher level and are less trying to squeeze out every last bit of the "simplistic" hardware.