Silent Hunter 2 earns points for being a good, realistic sub sim, but I have two chief complaints. First, career mode is formed out of scripted missions, which feel more like problems to be solved than actual wartime encounters. Second, any time you can see an enemy they can see your submarine, which makes historical night torpedo attacks on the surface impossible. For these reasons, I think Silent Hunter 3 to be superior (even though SH2's interface is much less pointlessly confusing.)
