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