Dwarf Fortress

"Dwarf Fortress is a single-player fantasy game. You can control a dwarven outpost or anadventurer in a randomly generated, persistent world.

Although Dwarf Fortress is still in a work in progress, many features have already been implemented."

• The world is randomly generated with distinct civilizations spanning centuries of detailed history, hundreds of towns, caves and regions with various wildlife.
• The world persists as long as you like, over many games, recording historical events and tracking changes.
• Command your dwarves as they search for wealth in the mountain.
• Craft treasures and furniture from many materials and improve these objects with precious metals, jewels and more.
• Defend yourself against attacks from hostile civilizations, the wilderness, the depths, the dead and creatures of the night.
• Support the nobility as they make demands of your populace.
• Keep your dwarves happy and read their thoughts as they work and relax.
• Z coordinate allows you to dig out fortresses with multiple levels. Build towers or conquer the underworld.
• Build floodgates to divert water for farming or to drown your adversaries... and don't forget the magma!
• Surgery, sutures, splints, crutches and more: care for your wounded dwarves instead of leaving them to fend for themselves."

Dwarf fortress is a good game for me to look at, it is heavily focused on each game, and each player getting their own generated world, that is completely different to that of any other player. To do this the engine creates new lore for each game started, which depicts the entire back history of that world. This is interesting to me as I want to focus on the lore of my own world in an effort to make the deeper meaning of my story more easily accessible to the player.

http://www.bay12games.com/dwarves/features.html