Crusader Kings 2 is easily one of the most enthralling strategy games on the market. That should be no surprise. As the guys over at Paradox Interactive have a great track record for making quality video games like Europa Universalis, Hearts of Iron and so on. However, Crusader Kings 2 goes above and beyond.
Not only do you play as a country in Crusader Kings, you play as a king. The game isn't so much about managing a country, as it is about managing your family. Sure, you gotta make sure to win the wars and defend your borders. But you also have to make sure your evil brother isn't plotting to kill you so he can claim the throne for himself.
This game is deep and has a steep learning curve. But trust me, once you get into the game and start building your own dynasty, you wont want to stop playing.