Unless lots of people are thinking that the poll is Japan only, I'm surprised by the number of people voting for FFXIII. Even in Japan with NSMB Wii having a full month, and FFXIII only a couple of weeks it will be close, but worldwide I dont think FFXIII in Japan only has a chance.
I think Worldwide December totals will be NSMB Wii> Modern Warfare 2 > Wii Fit Plus > FFXIII > Assassin's Creed 2.