Battlefield 3 hands down.
These games were made for 2 different reasons.
Battlefield 3: Create a well polished revolutionary game that would be the successor to Bf2.
MW3: Pull something out of there asses so that Activities would make infinite monies.
The truth is, Call of Duty is just a brand name to make money.
In fact, mw3 uses the same engine Cod2 did.
Just a new story new guns new perks. OMFG GHOST SO KEWL.