Inb4 megathread?
On topic: I never played the Battlefield series, but BF3 really intrigued me, its a step away from that super fast paced action that you get with the Call of Duty series. Of course, Halo was my go-to FPS when I wanted a slower pace, but BF offers a somewhat slower experience than Halo, and on a larger scale.
Btw, when I say slower paced I don't mean it in a negative way, I just mean your not constantly getting adrenaline rushes (which can sometimes wear you out really quick depending on how your day is going), and that your actions are more important.