I shot four missiles, so I don't know what to say. I suppose I enjoyed the first move I made. Then, when I realized the person that I asked to ally with was dead and the other three people were all allied, the fun factor sort of disappeared.
Most people don't fight wars by just tossing nukes around. It may be difficult to implement (unless you just want to copy Risk), but NBC infantry, armored divisions, and other such units should be added.
Perhaps government should play a little bit of a role. With democracy, your soldiers have +1 attack, while with communism, you get twice as many soldiers. Those specific examples may be unbalanced, but I think you get the point.
Do it on Earth again. Maybe you can incorporate the Moon as another area you can fight on (Of course, only once you've developed a space program).