I have been playing Dwarf fortress on and off for a few months now. The learning curve is brutal. I probably spent 6 hours watching u-tube lets play videos before I had a good grasp on the early portion of the game. The UI is complex the options are arcane and the play can be buggy. I think it might be the best game I've ever played. While technically not a 4X game I think it's main appeal is toward people who like Civilization type games.
If you are interested I'd suggest downloading the Lazy Noob pack http://www.bay12forums.com/smf/index.php?topic=59026.0
Reading this tutorial http://afteractionreporter.com/2009/02/09/the-complete-and-u...
and prepare yourself for some fun (fun means death).
Have tried so many times to pick up that game. I don't have the fortitude of patience needed to grok that game outside of reading other's accounts.
Dwarf Fortress is a lot older then Minecraft and I feel like the two can't really be compared. It also doesn't require a good GPU which makes it perfect for playing on the go! I always keep it on my phones SD card so I can just plug my phone into any random old computer and play it from there.