I remember when you could strafe run in BC2. xP They were pretty quick to patch that out of the game. Personally my core reasons for liking BC2 (and battlefield) over MW2/BO (and CoD) are two things:
Teamwork. Yes, you actually have to use it in BC2, you can't have one person win a game for your team no matter how good they are.
Uniqueness. It's different, new, exciting. "Oh no someones hiding behind that wall to ninja me when I run around this corner" *I proceed to blow up the wall killing the camper in the process*. "Ahhh my base is being raped! But someone managed to sneak past in another squad." *I proceed to switch to his squad, spawn, switch off (leaving room for others to spawn out of base), and go in behind the spawn campers to break their lock down.*
BC2, is the closest thing I've seen to eliminating base rape, and camping I've ever seen. I've played on 2 or 3 competitive teams in it and really enjoy every aspect of it (except "Snipers", learn2play Recon and help your team!). Me and my friends/clan (vV) actually ran the 5th most popular server in bc2 for quite some time.
Also, thoughts on ArmA 2? I've been thinking about picking it up next time it's on sale, as it also seems to be very unique and strategic.