COD has a ton of mainstream hype, while I see little mainstream hype for Battlefield 3.
Battlefield has far more hype among gaming sites and hardcore gamers, however we all know there are far far more casual gamers who only 1-2 games a year and what do they buy COD.
Also about beating Black Ops, we said the same for that game.
Also remember COD sell really well up till spring unlike hardcore games like Gears of War 3.