PS3 - GT5, easily. Assuming it isn't delayed to 2011. It could easily do close to 2 million first week and if its released in Fall then 6 million by years end. My prediction anyways.
360 - Halo Reach. It has Halo in the title.
Wii - Wii Fit 3, just kidding. Probably Galaxy 2. It sould do nicely.