5. Europa Universalis IV
Europa Universalis IV is the fourth game in the long-running series of ultra-hardcore strategy titles by Paradox. Certainly, the studio has made numerous spin-offs like Crusader Kings, Hearts of Iron, and Victoria, but their core creation has always been Europa Universalis.
The newest title is set to begin at the end of the Middle Ages—during the dawn of Age of Explorations—and end in the late 18th century. It's expected to be larger, and more detailed than any of the previous games.