Shows what decent marketing can do. Sony managed to encapture exactly what makes Uncharted so great via its ad campaign (it's like a movie! but you play it!), and between the ads, the contests, and other promos, Uncharted 2 received far more attention than the original Drake's Fortune. Left4Dead 2 is showing similar gains over its predecessor for similar reasons. Valve really stepped up their game with that one.
It looks like Sony is going to be pushing God of War III as heavily as (if not more so than) Uncharted 2, if the God of War Collection, God of War III Ultimate Edition, and apparent limited edition bundle are anything to go by. Assuming the game stands up to the first two, I wouldn't be surprised to see God of War III hit 3.5 million, besting the sales of the original.
I'm glad Sony is finally giving their games the attention they deserve. I honestly think LittleBigPlanet was advertised better this past holiday than it was when it was released. Games can be the darling of trade shows all they want (Killzone 2), but in the end it's the mindshare of the public that matters most.