I've been playing Europa Universalis III for the past week and I can't get it out of my brain. General idea: you pick a country in 1453 and play it through 1789, doing pretty much whatever you want. Despite the title, you don't have to pick a European country. The problem for me is that playing day by day for 300+ years of history requires a tremendous amount of thought, and the stupid game has basically been churning in my head non-stop for days.
I'm still on my first game, having started as the single-province country of Leinster on the island of Ireland. My first goal was obvious: take over the other four Irish provinces and unite the country. Sounds easy, right? Except that Meath was controlled by Britain, and the other three provinces all allied with each other and whenever I'd attack one the other two would jump on me. So I had to use diplomacy to turn two against each other, and once they were fighting I attacked the third. The two warring provinces were easy to mop up, but what about Meath? Britain would crush me like an ant, so I had to incite rebellion in their Irish stronghold and convince the superpower to cede the troublesome province over to me. After several days spent conquering Ireland, then what? Why, off to Italy to vassalize one of those rich trading nations, like Milan.... Now that I've subjugated Milan and annexed another nearby Italian province after a war with Rome, I need to figure out how to take Rome itself....
Anyway, it's ridiculously complicated and therefore agonizingly fun for an OCD gamer like myself. If you're into history and strategy games, you won't regret picking up a copy for yourself. And don't forget to check out the EU3 wiki for some helpful tips, you'll probably need them.