To put this into a comparison, here are some of the other best sellers in their first 52 weeks. These are all estimated with the graph tool, and may be up to 500 thousand off.
Call of Duty: Modern Warfare 3 - 27 million
Call of Duty: Black Ops (Ps3 + X360) - 23.8 million
New Super Mario Bros. Wii - 16.8 million
Wii Sports Resort - 16.3 million
Wii Fit - 15.8 million
Mario Kart Wii: 15.1 million
Grand Theft Auto IV: 13 million
There are a few ways to view this.
1) Can Grand Theft Auto V sell as fast as the fastest selling Call of Duties?
2) Can each individual version of Grand Theft Auto have nearly as good a first year as Nintendo's top titles?
3) GTA V will most likely sell 8-10 million first week. Mario Kart Wii did 1 million. Can GTA V's week 2-52, all versions combined, manage to match Mario Kart Wii?
The third one definitely sounds like it should be possible. The first way of looking at it also makes it sound possible, and I don't see why the second one should be impossible either.
I think 25 million is a perfectly reasonable prediction.
