I'm casting a vote for Battlefield. Not to jump on the whole "lol cod sux forevur" bandwagon, but because I've always been a fan of BF and it's Conquest game mode, rather than the standard death match that many games already have. I for one actually liked playing through the Call of Duty series (or at least the single player campaigns), so I'm not 100% sure where all the CoD hate comes from. The multiplayer community? Because it's overrated? Because everybody else hates on it?
Also just going to throw this out there.
Battlefield 3
+Destructible terrain
+Drivable vehicles
+Conquest Gamemode
+Large maps BECAUSE of the Conquest Gamemode
Lol. Call of Duty has to be the cheapest FPS out there, at least other games attempt to have some sort of balance.