This year, Sony have had a tonne of core exclusives and a price drop without Microsoft really doing anything other then the normal exclusives and they can't beat 360 consistently on a week-to-week basis.
In the core genre's of RPGs and Shooters 360 is dominating. Also on the casual side 360 is doing well. Kinect is still in the top 50 and Lego Harry Potter on 360 outsold even the Wii version.
Sony consistently has to have some concerns. Move is dead. A price drop wasn't enough to hold #1 in sales through the holidays. Also, Uncharted 3 is ok, but it should be exceptional in sales.
Think what you want about Microsoft, but they are outmaneuvering Sony on the marketing front every step of the way this generation.