How do you keep your game interesting?

For me playing the decades challenge (my own style) has made the game very interesting. I keep having to find ways to incorporate history into the game and work around it which makes the game more interesting. For instance one character suddenly had a crush on her best friend, and this in a time when homosexuality wasn't legal, so then I had to figure out how to work with that element in game and think about the possible consequences. Then you have to work in all the major events into the game, so how does WWI or II affect the characters? Who goes, who stays, who lives and who dies? For me it's enough to keep me interested, especially as I play the game semi rotationally, so that I can get as many aspects of history in there.