Let's call it "voxel style graphics sandbox games"

If you are afraid of making something people will be bored with, you can always try something original

An option might be to replace the graphical style, then you end up with a sandbox game where you have to invent other ways people can be creative. Perhaps you can let them pump up oil that is used to mold plastic objects. Have this little crafting interface which is a very simplified 3D modelling tool.
Make sure people can easely put up screenshots or youtube video's of their creations, because the whole purpose is to show off your creations

Or replace the "sandbox" part and make it a race game (cars with square wheels, must be funny), an fps or a tycoon game perhaps.

Let's called it "voxel style graphics sandbox games"

If you are afraid of making something people will be bored with, you can always try something original

An option might be to replace the graphical style, then you end up with a sandbox game where you have to invent other ways people can be creative. Perhaps you can let them pump up oil that is used to mold plastic objects. Have this little crafting interface which is a very simplified 3D modelling tool.
Make sure people can easely put up screenshots or youtube video's of their creations, because the whole purpose is to show off your creations

Or replace the "sandbox" part and make it a race game (cars with square wheels, must be funny), an fps or a tycoon game perhaps.