asc99c on 12 December 2009
I'm not sure release date matters as much with a title like GT5. I expect this to have a really long tail of sales. Look at GT4 sales:
http://www.vgchartz.com/swlaunch.php?reg1=All&game1=Gran+Turismo+4+-+PS2[887]®2=All&game2=®3=All&game3=&weeks=250
The US launch got it to around 4,000,000, but then throughout the rest of the first year, it made another 2,000,000 and another 2,000,000 the year after. It even sold 400,000 units in the 5th year after release. It's showing as selling 6,542 copies this week(!)
A holiday release is only massively important if the game is sold on hype and reviews don't match.
