Let's face it, Resistance is a good game but it is not a hype/system seller type of game like Gears Of War.
Neither is Motorstorm, and LBP is a new franchise.
It's not surprise for me that neither R2 or LBP are selling well at this moment.
But when we think about MGS4, now, that is a big, big system seller, so it sold really well (or GTA).
In the next year, it's easy to predict big sales for RE5, God of War or GT5. These are very strong established franchises that will sell millions of copies easely. Probably when GOW releases the PS3 will see the biggest boom in sales since it launched.
As for Killzone 2, unfortunalety I don't think it will do extremely well. I think it will do just well. Killzone 1 was a good game, but Killzone is not a strong franchise and has only 2 titles released.
Just needed to point this out, see while MGS4 did well, GTA4 despite being multiplat did not do as well as previous GTAs that were made only available for PS2 before the ports.
Gears of War however was helped in hype, marketing, evangelizing due to Epic Games's experience in marketing Unreal 1, 2 and the UT games on PC over the internet (basically reapplied to console 360) but more over they were helped by tv channels dedicating 30 to one hour informercial documentiaries to help sell the game with the Sci Fi doc, G4TV's ever constant free advertising for Microsoft XBox only games.
My friend who has On Demand from comcast is constantly complaining about how ridiculous it is that GoW2 is constantly popping up in the pip box as something people need to see or know about, to me at first it seemed like just business but I admitted it was extreme because it is constantly looping so short of saying that G4TV is somehow owned by an affiliated company you can get an idea of why its presence is felt even with people who don't care and why Assasins Creed really sold 7 million despite being a mediocre effort.
However, RFoM sold mostly to the tune of 2 million on a Playstation branded console that is not really associated with FPS shooters only console box so Resistance 2 is guarranteed to simply sell 2 million units to those who played and liked the first one, after that its going to depend on new PS3 owners who recently bought their console and its up to them to buy the game since no one is spoon feeding them a constant presence to buy the game.