Advance Wars DS 2: Map sharing, voice chat, ONLINE BATTLES

Okay, I'm completely sold. Initially I thought Advance Wars: Days of Ruin would probably sell less because of the gritty design, not-so-happy atmosphere, and loss of all previous characters (not to mention the loss of 'Dual Strike' and general toning down of CO powers), but Intelligent Systems knows what really satisfies their customers. Map sharing is pretty kickass enough, but online battles and voice chat (via the Nintendo Wi-Fi connection) takes the entire cake, eats it in one bite, and takes another one. If you don't have a DS, you'd better get one because this is gonna be the best thing to happen to it since EBA. Read Kotaku's hands-on impression of the game.

Fans are already making custom maps, and even entire campaigns. You'd have to register on that site to submit your own custom maps but it's free.

On an extremely related note, there's an English-language trailer available, as well as some gameplay videos. Be sure not to miss out on the awesome.