Rename: Modern Warfare 2

As much as Infinity Ward would have liked to have dropped the Call of Duty name, Modern Warfare 2's full title is Call of Duty: Modern Warfare 2. 
 
This looks to have been altered more recently, don't see why, there're no two ways about it, "Modern Warfare 2" should be an alias only.

I always thought this too.

We've been through this many times. In all official press releases from both Activision and Infinity Ward, they refer to the game as "Modern Warfare 2", and we reflect that with our naming of it on the site. The call of duty branding is on the box, but is not part of the games official name.
 
EDIT: Here is the official statement from activision which they issued directly after the box art displaying "Call of Duty: Modern Warfare 2" was released ( source): 

Infinity Ward’s  Modern Warfare 2 is the direct sequel to  Call of Duty 4: Modern Warfare.  We have focused our attention on  Modern Warfare in order to most effectively communicate the fact that this is the first true sequel in the  Call of Duty series.   Infinity Ward, the original creators of the  Call of Duty franchise, has said from the beginning  Modern Warfare 2 resides in the  Call of Duty universe.  This is reflected in the title’s package. 

It should also be noted that "Call of Duty" does not appear on the Hardened or Prestige Editions.