Call of Duty: Modern Warfare 2 releasing this November, Activision is getting ready to position it as the "biggest selling video game of all time." I think they mean biggest launch, as I don't think it will ever overtake, um, Super Mario Bros. (40.23 million) or Nintendogs (21.67 million).
The biggest launch honor currently sits with Grand Theft Auto IV, which moved 3.6 million units in the first 24 hours and generated $500 million in sales in the first week. That might be beatable by Modern Warfare 2.
Activision's Call of Duty brand manager said that the company wants "to propel this year's title to be the biggest selling video game of all time. That may raise some eyebrows, but step back and look at the franchise's trajectory through preceding launches, and this objective starts to look viable."
Consider my eyebrows raised. There is no doubt that MW2 will sell extremely well on release, but "biggest selling video game of all time" is not possible.