Crysis, looking better than all games since 2007. Obviously MW3 was going to sell more copies, it is the arcade game of FPS shooters, aimed at younger audiences and is the product of massive hype and big money advertisement. BF only really became a big name franchise after BC2.
Either way, MW3 is a repackage of MW2 with some new maps and some tweaks, graphics are the same and the gameplay style is the same. It is a formula that works but to be honest it isnt surprising that it scored so bad in reviews on average as it is in no way innovating, low quality graphics and weak sounds.
But, like in racing games the arcade game is more friendly to a bigger audience and with the support of massive hype and advertising campaigns it isnt surprising that MW3 outsold BF3 and I don't think anybody expected otherwise.
MW3 is arguably the biggest release of the year. Yet it is the only release that hasnt made a leap forward in graphical technology. The Original Crysis of 4 years ago still looks better in every single aspect, Crysis 2 made leaps with its engine and BF3 has made some awesome improvements (BC2 already looked better than MW2, and still looks better than MW3, atleast on PC). Graphical development isnt the end of the world though and a game doesn't need it to be good, but we come to expect graphical advancement and to not see it from the biggest game release of the year when its main competitor has done in a big way, it is a disapointment and it shouldn't happen.