On One device only.

Call of Duty: Ghost (Xbox 360)?

Animal Crossing: New Leaf?

Pokemon?

Grand Theft Auto V (PS3)?

FIFA 14 (PS3)?

Other?

Animal Crossign already have 2.1 million with six months to go! (We'll not count what it sold last year in Japan. We'll count this year only.)

Call of Duty and most of the other games sell less per console because of next generation.

We are talking about VGChartz numbers. Digital download sales are not counted.

According to VGChartz:

Best Selling Game of 2012: Call of Duty: Black Ops II Xbox 360 (10.8m)
Best Selling Game of 2011: Call of Duty: Modern Warfare 3 Xbox 360 (12.6m)
Best Selling Game of 2010: New Super Mario Bros. Wii (10.9m)

Pokemon X/Y or CoD: Ghosts

EDIT: Counting Animal Crossing would be pretty unfair, it already released last year in Japan.

On which console?

Please, state on which device or your vote will not count when I do the chart when this thread die.

Grand Theft Auto V (PS3).

Edit: Not sure whether it'll be going in the favour of the PS3 or the 360.

I forgot that it released in Japan last year. It sold 2.1 million this year. I'll fix it now. Thank you.

I'd say it comes down to Cod, GTA and Pokemon X and Y, if you count both Pokemon X/Y as one then I say that will win, if not I say the PS3 version of GTA 5.  The PS3 version because you need 8GB to install it on 360 and memory on 360 consoles is more scarce than on PS3's MOST of the time, but who knows the 360 version might well better.

^^
Yes, Pokemon X/Y will count as one game.

GTAV - 360
And there's a chance GT6 will sell well.

Grand Theft Auto 5 on the PS3.

Releasing nearly 2 Months before Call of Duty and the PS3 version of GTA has a bundle.

Edit - And Ghosts 360/PS3 will have competition from Ghosts PS4/One.