Well, both Motorstorm and Resistance were the first games right? And they even sold with the consoles, so them being that "high" is expected.
GT5 and MSG4 are popular series, so that's also expected.
I guess LBP will have a lot higher numbers, atleast here in Norway LTB is 24/7 on the telly, and it looks like a "kids" game, so probably a lot of parents will buy it for their kids with a PS3.