The first in a long line of great GBA stategy games.
I actually received Advance Wars by chance on one Christmas. My aunt and uncle have a tendency of buying me random GBA games without knowing what they are, and I recieved this with less than enthusiastic response. I mean, really, how good can a GBA strategy game really be? The answer: really, really good.
Advance Wars takes place in a world called Cosmo Land, and follows the story of 3 COs (basically generals) in the Orange Star Army, one of 5 opposing forces in a war that seemingly popped out of nowhere, with no reason. As the story progresses, the truth behind the real nature of the war is revealed, and the real villian is introduced, who is maybe the worst Darth Vader ripoff I've ever seen. The story isn't the main selling point here, but the characters are somewhat interesting, and you care what happens to them in the end.
Advance Wars' greatest strength lies in its excellently balanced gameplay. The battles take place on a typical square grid, varying in size from mission to mission. Controls are simple, with the A button selecting units and the B button deselecting options and showing enemy movement range. Attacking is simple, just move your unit into range and choose fire. Unit maufacture is also simple, with no multiple unit requirements or complicated tech trees. Just build a factory, airport, or seaport and pay for your new unit. The real beauty of the gameplay system is the perfectly balanced unit types. Each unit has 10 HP to begin with. The units work in sort of a rock/paper/scissors format. Tanks can decimate infantry units, fighter planes can knock bombers out of the sky, and armored infantry can take on recon units easily. Each unit has another unit it is weak against, and one it can dominate. This system makes for great strategic moments, and a real sense of accomplishment when you have a great strategic victory.
The game's difficulty isn't too bad, but it does take some planning to win some battles. At the end of each battle, you are given a letter grade rank and a number of coins which can be used to purchase extras. My only gripe with the entire game is the insane ratcheting up of difficulty in the last two missions of the campaign, which had me throwing my GBA against a wall in frustration. The final battle has you suddenly taking control of multiple armies, and I believe the game should give you some practice with this mechanic before throwing you into the hardest battle in the game with it.
The main campaign consists of 17 missions, with branching paths depending on which CO you choose to control in certain missions. Once you beat the main game, you can unlock the Advance Campaign, basically a Hard difficulty. While this may not seem like a huge number of maps, the real replayability comes into play outside the campaign. There is a War Room mode in which you can play 20 new maps against the computer. Then there's the multiplayer mode, which features over 100 maps to unlock with your coins from the Campaign and War Room. These are the real meat of the game, especially if you have someone else to play with.
If your GBA (or the GBA slot of your DS) is gathering dust and you're looking for a great gameplay experience for a (presumably) bargain price, you can't go wrong with Advance Wars.