I think SONY's first party lineup suffers from mediocrity.
Their games are good, but they aren't special.
Uncharted is a pretty Tomb Raider with some Gears of Wars and PoP. The game is excellent, but it does nothing new.
Killzone 2 is another shooter; a great one with pretty graphics, but nothing that haven't been done before (and this generation has delivered in the same genre a lot of games).
Ratchet and Clank is the same old Ratchet and Clank with better graphics.
Wipeout is the same.
Resistance is the same as Killzone.
Motorstorm is your average racer with awesome physics and graphics. Hell, most gaffers prefer the superior Excite Truck to this (which is a lot more original).
And I could go on and on.
The only "different" (retail) game they have released is LBP, and it failed to do anything because it was released to a userbase accustomed on getting more of the same with better graphics.
The difference with Nintendo's games, is that Nintendo has been disruptive this generation.
They have this awesome Wii Fit software (that was not cheap to make); that is so successful that even my mom talked to me about the Wii and Wii Fit (she has never even mentioned a console before).
Wii Sports and Wii Play are little experiments that changed the way we play many successful or not types of games.
You have the old games with some sort of special add on, that have been greatly successful (Mario Kart, Wario Ware, Mario Party, etc).
Then you see the games that are more of the same, but better, the "core" games (Galaxy, Fire Emblem, Smash, Zelda, Metroid, etc) and they have sold a comparable amount of what those series always sell.
And you see people preferring playing sports games with the Wii remote (Tiger Woods is a good example). Also there are two big companies right now fighting for the next big hit tennis game on the Wii.
You see people preferring the Wii versions of snowboards games (Shaun...) because of the balance board.
You see, the problem with the PS3 is that the only new things it brought are a good (not great) and free online infrastructure, and Blu-Ray playing capabilities, and most of the games suffer the "most of the same with better graphics" stigma (deserved).
In the end, the people have spoken. Wii first party lineup is by far the best and it is not even a close contest. Fight for the second place.