Open ended city-building simulator. Minecraft meets The Sims, with a difficulty level that can only be expressed through swear words.
Slaves to Armok: God of Blood Chapter II: Dwarf Fortress is a part roguelike, part city building game. It generates a high fantasy world using fractals and mathematical techniques so that each world is completely different. Like most roguelikes, Dwarf Fortress is text-based but don't think that means it's light on computer resources. DF is the most complicated and in depth game ever. Tarn and Zach Adams have worked on the game since 2002 and plan to work on it for another 20 years before it comes out of alpha.
Pro Renowned for depth of simulation and emergent gameplay
The ultimate goal of Dwarf Fortress is no less than a total fantasy world simulator. Its simulated systems include geology, metallurgy, fluid pressure, temperature, combustion and phase transitions (melting, evaporation, etc.), shear and tensile strength, ballistics and gravity, anatomy and tissue damage, growth and maturation of animals and plants, emotional states, life goals, and alcohol dependence.
Pro Massive randomly-generated worlds persist across multiple games
Estimating one meter per tile, the smallest possible Dwarf Fortress world is roughly 13 kilometers on each side, and about 400 layers deep. The largest world is about 197 kilometers (123 miles) on each side. Each world has its own randomly-generated history with thousands of notable figures, warring factions, and numerous settlements of various races. Any number of fortresses and/or adventurers can be played in a particular world, though only one at a time.
Pro Base game is free (supported by donations)
From the Bay 12 Games donations page:
Bay 12 is dedicated to providing original games free of charge, but that doesn't mean it is free for us to make them. We've been online since December 2000, and you can help Bay 12 Games continue to thrive. If you've enjoyed any of our games, and you are able to give, we accept financial support.
Pro Lots of ways to die, no way to win
Starvation, riots, goblins raiders stealing your babies, goblin war parties stealing your lives, elephants, vampires, werewolves, werebears, werebadgers, carp, digging into an aquifer, digging into lava, digging into the nesting area of a Forgotten Beast, selling wood to hippies, insanity, drowning in knee-deep water, and being attacked by your own dismembered finger.
There are a lot of ways for dwarves to die. Age really isn't one ever heard of. After playing this game long enough, you'll realize why dwarves don't like going outside. Everything from harpies to dangerous man-eating carp is everywhere. Some of them are humorous, but most are a lesson.
The entire game acts as a massive learning experience. Don't tell your dwarves to fish; they don't know how to swim. Wall off your fortress or a necromancer will make your lunch attack you. Don't dig too far down, or something scary will follow you back up.
There is no victory, only glorious deaths. What goals you set in the game are up to you. Make small, simple goals that you know you can complete. "Surviving for 100 years" is like "curing cancer". Not technically 'impossible', but it might just be easier to settle on building a bridge for now.
Con Controls are complex and often counterintuitive
New players are advised to read the Quickstart Guide.
Dwarf Fortress takes a lot of patience to learn. Even something as basic and early as world creation might take a guide to understand the first time around.
It doesn't really matter how experienced of a gamer you are; if you try to play this game without a guide, you're going to have a hard time.