1st, Uncharted is not that big franchise, it makes sense it has smaller number than Battelefield, Skyrim and Assasin Creed
2nd, Battlefield 3 preorders outpaced Black Ops last year according to many retailers, and the projected sales for Battlefield 3 is 11 million copies from EA
3rd, Assasin Creed's preorder number has already crushed AC: brotherhood last year.. AC franchise is big in Europe and this is North American chart
The most sales of Elder scrolls and Mass effect games are from North America so this makes sense