Over 40 million gamers are playing one of the releases of Call of Duty. Discussed during the recent Activision earnings call, the breakdown of monthly active users in December by title for the five most recent releases are:

- Call of Duty: Modern Warfare 3 - 20 million
- Call of Duty: Black Ops - 10 million
- Call of Duty: Modern Warfare 2 - 5 million
- Call of Duty: World at War - 1 million
- Call of Duty: Modern Warfare - 1.5 million

To underscore that Call of Duty is a "main stream" game, the critically acclaimed and popular Battlefield 3 has around 6.5 million monthly active players.

Source: Activision Blizzard Earnings Call Transcript

Cod4 still the best!! Thumbs up for Asylum Project Team!

Im sure if players could give away their cdkey much less games will be sold.
smart how produsers are working together with STEAM.
Now Blackops 2 can be pre-ordered. on the website it doesnt say "BEWARE ONCE BOUGHT ITS YOURS FOR EVER" you cant give it to friends or even to your own family.
While European law says, when a game is bought, the owner may do with it what he wants, give it to others, sell it or burn it :)

Another thing... DONT BUY BLACKOPS 2 from steam, on the net there is already a price difference of 50%. just so you know :)

Now Black Ops is pretty popular due to the near release of Black Ops 2.

I'm going to disagree with this. Call of Duty Modern Warfare is still very popular. I play on a server called Fusion Gamers on COD4, and everyone says COD4 is the best. I agree, I still play Modern Warfare 3, and Modern Warfare 2. A lot of people says MW3 sucks..

Funny, I believe that CoD4 has STILL more players than BO and MW2.