The single player stands apart with its open world, but its the multiplayer that really does it for me.
the thing i like about the multiplayer is that its almost impossible to "camp", which is one of my biggest gripes with online shooters. i say its impossible because theres no where to hide! say somebody sees you in your sniper tower, they can just smash the tower to the ground. or maybe you could strategically place remote charges on a bridge, and take it out when an enemy is passing. its things like these that always make the only experiance unique, and you always see something new.
the single player is also great. unlike most shooter single players, you arent told directly where to go, and you dont have to do whatever the game tells you. it has a more open world gameplay style, which i think is way more fun. the single player also implements the destruction factors, which never get old.
basically, this is an awesome game. whether or not you play single player, or even better, online, your sure o have a fun experiance, if your tired of the generic shooting games.