'Call of Duty 4': Most played Xbox Live game

The best-selling Call of Duty 4: Modern Warfare is now officially the most played game on Xbox Live, according to stats by Major Neison.

The popular first-person shooter knocked the long-running Halo 3 into second place during the week ending January 21.

Statistics are tracked by the number of unique users logged in to Microsoft's Xbox Live service that are playing any particular game.

As well as enjoying the top spot, Activision also has the third most popular title on the service, with Guitar Hero III.