Advance wars. Normal campaign is pretty fun. But it's the advance campaign that'll give you the most enjoyment, and possibly, frustration. If you're into strategy games, this is the way to go.
If you can beat advance campaign for AW1, hard campaign for aw2 should be easy.
Also, fire emblem. The japanese versions have advance campaigns too. It's awesome.
Human history is the story of complaisance. While disaster is fresh in our memory, we take precautions. But as the memory of disaster recedes, we start to take risks.