I love beautiful environments and such, so if I could pick anything that wouldn’t exists based on something that does exist, I would make a 3D or even VR version of this old Korean 2D sidescrolling game called Maplestory.
Not gonna lie, that’s going to be 99.9% nostalgia, but it has a couple of awesome areas that have amazing backgrounds and thoughts behind it. Like typical magical forests, dungeons, cloud cities, but also a lego-gone-interdimensional city where time is weird.