What if the world ended tomorrow?
Create yourself (or whatever you want, if you're a party pooper) in the character creation stage, to see how YOU will fare in an end world scenario. With a very detailed character sheet and character quiz in, create yourself as close as possible, including information like: country, languages, professional and educational resume and personality.
After character creation starts the world generation stage, where it will simulate the world ending (with a selection of different moddable ways: alien invasion, armageddon, meteorite hit, zombies) the next day. Then (because it will be hard to simulate the whole world), you will be thrown in a "getting lost" scenario (plane crashing, vcation trip on a boat, but it will always be on an island or island group, so it can be easily simulated) which will put you somewhere proceduraly generated, with random environments and other people, and see how you survive.
The game is handled similarly to "Crusader kings 2", where the locations and things on the map are resembled in a pretty abstract way, with a great emphasis on character relationship and interaction, you will have to manage resources, mange people (if they will listen to you...), crafting items and the usual things, to try and stay alive.
A variant of this would be a low fantasy world where you form an expedition to a new land, you need to manage your settlements and send adventurers to explore dungeons. an highlight of this variant would be sending a group the a certain dungeon to kill the unique white Minotaur, taking the corpse back to the settlement so the blacksmith can powder his horns to mix them with steel and make a magical weapon, and a witch using the creature's heart for a dark ritual.
i can expend on this because it's an idea i have been having for a long time and would really want to make it happen