2D Metroid of course.
More in what I dream would happen, and have since the Wii was announced, is a game that would fully realize the Battalion Wars/Full Spectrum Warrior concept. I play as whatever soldier on the top screen but also issue orders to other soldiers (and jump to them in the BW style, or not in the FSW one) through the touch screen. The Wii would have been a much better option but I'll take whatever I can on this front.