1. the player explores the world they know from a new angle, now devoid of human life but deadly
2. this world is now filled with treasure, food, water, medicine etc.
3. where treasure can be found, there is also danger
4. most treasure is found in urban areas, which are also the most life threatening (intrinsic risk vs reward structure)
5. the setting has room for humor (excludes many realistic events like war, drought, exodus, anything potentially too close to home)

Apocalypses can happen for a number of reasons, none of which necessarily contain zombies, even though people seem to like to insert them anywhere.

Any apocalypse scenario should work? Just skip the zombies.

Maybe not even explain it, it can be a huge mystery wtf really happened....

"the setting has room for humor (excludes many realistic events like war, drought, exodus, anything potentially too close to home)"

Apocalypses are not really fun. Thats why inserting humor in them makes for good comedy. The darker the better

The thing with apocalypses is you have all those things at the same time, wars, drought, exodus, ( and evil bastards, heroes, suffering, hope, despair, insanity, clinging to the "holy", etc, etc) because everything went to shit... its an intrinsic part of what an apocalypse is.

Alien invasion, robotic uprising, interdimensional rift spawns Lovecraftian horrors, re-emergence of mythical creatures, Mad Max style social breakdown (global warming, nuclear war, technology fails, ...), mutagen run amok, wildlife turns on humanity, ghosts attack, battle between heaven and hell rages on Earth, vampires enslave humanity, secret lizard people running the government reveal themselves and begin eating everyone, humans are somehow shrunk to the size of an ant

A bunch of scientists in New York working on time travel accidentally send themselves 150 years into the future, New York is overgrown and junglely, they have to travel through New York to reach a beacon that indicates there might be civilized civilization at that location. The goal is to travel through jungle'd New York, avoiding bandits, tigers, bears, etc... and make it to the destination. Because of the state of New York, collapsed buildings might block the most straight-forward path.

Infact, you could hand-craft the entire game world has a 7x7 grid of regions and events, and then randomly generate a path visiting the cells of the grid, and that's the route the player has to travel to the destination. Harder difficulties could make the path extra long.

I always thought it would be interesting to set the apocalypse to have happened at an earlier time. For example, what if something apocalyptic happened right before the start of World War II? (or sometime during it) You could have a small band of semi-international soldiers trying to head someplace that might or might not be safer.

Forget the zombies, just survive your family.

Modern Oregon Trail:

A career opportunity for a lower middle class family requires that they move from the east coast to Oregon. With limited budget and limited time, you are tasked with hauling your family and life's possessions across the country in the family station wagon / suv, that was purchased a few years before your teenage kid was born. Regular stops for food, sleep, comfort, and site seeing will be expected on the way. Random events including mechanical breakdowns, theft, construction and other road delays, family disputes and obligations, and other morale / comfort issues. A successful journey will be made on budget, on time, with a minimal loss of family treasures or family members and possibly (if you really want to get wild with the random events) a minimum of outstanding tickets, restraining orders, court ordered appearances, or warrants on all family members.

I think it'd be cool if you could customize the family members you have on this trip and it'd affect gameplay and difficulty in some way.