Dwarf Fortress is an ASCII game based around establishing and protecting an outpost of Dwarves from everything that wishes to kill you. The game is brutally difficult, it is less of a learning curve and more of a sheer cliff of difficulty and it is actually reccomended by the game that you have the Wiki open while playing.

These statements may make the game seem like more trouble than it's worth but it's possesses a very accurate geological side and you can do pretty much anything that you want with it. Plus there's the classic tale of Boatmurdered with psychopathic elephants, breaching hell and unleashing a demon, unleashing a sea of magma onto some invading Elves and Goblins and a former mayor of the outpost going berserk and beating a soldier to death while on fire.

I think Dwarf Fortress is an amazing game, I usualy use a differnet tileset though, the ascii gives me a headake. The learning curve is huge, but there are allot of good tuts out there to help you out . 

Anyway, i recommend people alteast give it a fair try.