Supreme Ruler, like Making History or Europa Universalis, is an extraordinarily detailed and complex grand strategic game covering the entire globe, with economic, military, and diplomatic aspects. As long-time readers may know, I'm a sucker for this kind of game.
Unlike the others, Supreme Ruler is set in the modern world -- sort of. It's set in a hypothetical near future, which is canny of BattleGoat but also somewhat disappointing; canny, because if you try to simulate the real world, you're always going to get flack on minute levels of detail (e.g., "I am from the country of Mystflx, but why don't you show the iron mines at Qwertyuiop?"), so it's easier to create a game that is representative, but not an explicit simulation. Disappointing, because playing around with a good version of the real world would be interesting.