COD definitely nails the movement and gun feel. This was especially noticeable going from COD to BC2 (BF3 feels quite a bit better IMO).
This may play a small role in why COD is popular, but I believe the accessibility (read easiness) is the main factor. No physicals, practically no recoil, and giant car-sized hit boxes are good examples.
After playing BC2, I just really couldn't go back to COD. It's such a shallow experience and really only supports one play style (run & gun). Whereas BF supports many different play styles and there's so much more to do and master.
When I first heard you always had to be online, I assumed every x number of minutes, it'd make sure you were online. Then I heard everything is saved in the cloud and realized it was more than that.
However, since playing the game, it's pretty apparent to me the game is ran on a modified version of the WoW engine and behaves overall like a MMO, client/server wise. This works out well for them since it keeps them in complete control and allows things like the Auction House to functionality similiar to in a MMO.
What it means to the average player is instead of thinking of it as a single player/coop experience, think of it as any other online game you've played in terms of your connection, just without any of the benefits of an MMO (aside from an auction house used to make Blizzard money).
Yesterday was the first time I played during prime time hours and it was pretty ridiculous lagging and rubber-banding around in a single player game. I get they want to protect their investment (I'm a developer myself) and want to prevent cheating/hacking, but they should have made sure they could ensure the average, non-cheating, paying customer's experience would not be impacted before going this route.
Want to combat used games sales? Next generation don't gouge storage costs and put games on XBL/PSN fairly quick after release with a reasonable discount ($10-20 less than retail). You're cutting out the retailer all together and giving your customers a break on price (probably matching or beating used game prices).
Dramamine0001's comments