I am on board with Dwarf Fortress for adventurer, first and foremost. I don't really like Fortress mode all that much, I'm more content to read the stories of thriving bastions in the middle of the darkness than actually forging my own, but while the game mode is limited now, the plans on the development page for Adventurer mode have me salavating. Even just the stuff that will be ready next release has me excited. When Dwarf Fortress is complete, it will boast one of the most immersive open world role playing games ever made (at least from the current perspective.) It will feature a truly unique experience with each world, and with each game. The incredible depth to the history as it is now, and the sheer amount of things you will be able to do is just mind boggling.
Adventurer mode's complete feature list looks like a single player DnD campaign with a sadist, blood-thirsty, but also unequivocally patient DM. He doesn't mind the detail of the world he has to create for you, and he won't gripe once if you want him to make a new one. He is just as content to cut down a hero of justice, as he is letting that hero cut down hordes of bandits and warmongers. He doesn't care and is just as satisfied to run a game if you want to be a hermit farmer content to simply feed yourself, or a caravan runner seeking to make your own fortune. He doesn't care if you are the 12th century equivalent to Indiana Jones, or the 12th century equivalent to Jesse James. He will be just as satisfied if you start with the blessings of the Gods, or the curse of being a mundane peasant. Pacifist or berserk. Honorable, or a bastard. King or slave. Hero or villain. None of these matter to our faithful game master. All he cares about is that you have Fun.