I did some calculations myself. I added up all the exclusives that have sold over 1 million and this is what it looks like:
Very very close, less than 1 million difference. I didn't include Kinect Adventures for obvious reasons or any 360/PC titles so that means no Gears 1, Fable 3, L4D1&2, Alan Wake, etc. Of course these numbers will change, but this is what it stands at right now.