The most popular games today are made up of mindless repetitive tasks, i dare say. World of Warcraft means slaying countless mobs in order to get gear and to fill some imaginary experience bar. Mining in Minecraft can occupy a normal persons attention for hours, even though it involves doing one thing over and over and over again.
What if we made a mindless game involving simulating simple real-world scenarios and rewarding imaginary points for actions? Perhaps a 2D-styled game like Terraria, where one could explore and build freely. When sufficient criteria are met, NPC's will spawn and live in the world with you. The NPC's can wander freely and manipulate their surroundings such as build new structures. You would be the town mayor since you founded the city.
I believe Minecraft (and other sandbox games) have taught us that building and creating is fun, ergo building a city is fun. If NPC's requests help in exchange for rewards (in-game gear and imaginary rewards such as XP), we would have a winning combination. Sandbox+Simulation+Addictiveness.
I'd love to see a game like that.