Super Mario Land
I redid the bulk of the graphics and injected it into the game using a tool that I developed. An IPS patch is available for download on the page.
The graphics are 2 bitplanes (4 colors) just as in the original, but you can choose your own palettes for foreground and background objects if you're playing the game in a more modern environment, giving you 4+4 colors, minus one for transparency.
It would most likely run on the original Game Boy (using a flashcart), but the original high contrast graphics were probably more suitable for that screen than mine are.