Hearts of Iron II

The Good
Great, if a bit unbalanced multiplayer. Very easy and very broad modability ensures that the game never gets boring if you find fellow WWII geeks to play with. The sounds in the game also work very well, bombastic classical music and proper sound effects for battles do wonders for the atmosphere.

The Bad
Do NOT buy this if you want a good single player game, the Artificial Intelligence is terrible (marginally improved, but still terrible). The peace treaties which AI can't handle are taken care of with events, which are unfortunately often very dysfunctional, ensuring that the what-if scenarios (say you've just conquered almost the whole Europe all alone with US, USSR has made peace with the Germans and has been beaten to the Urals years ago) don't really work (the moment Germany surrenders, the "Germany surrenders" event kicks in and the historical 1945 border is created, handing the whole eastern Europe to USSR), unless you code them to work on your own or try to find some mods from the large forum community at Paradox Plaza (current address: paradoxplaza.com). Needless to say, this kind of wrecks the whole point of the game when completing what-if scenarios almost never works.

The Bottom Line
It's a WWII geopolitical simulator covering the years 1936-1948, based on the original Europa Universalis engine. Very much like the other Paradox games before it. There is a world map (very much like one of a board game), divided on hundreds of provinces. Different nations and alliances try to grab as many provinces as they can as the game progresses. It's also a very "sandbox"-like game: it's very hard to motivate yourself to play if you aren't interested from the geopolitical schemes behind WWII, since the goals of the game are abstract and very far away: you don't get any rewards even if you "win" the game.