A lot of interesting discussions have already gone on about this game, whether it's Brainy Gamer or PixelVixen707, the argument goes like this. People love it because it's an open game that you can do whatever you want. People don't like it because it's an open game where you rarely feel inclined to do much at all.
That's a really important problem in a free form game because as emergent narratives become steadily more popular, you've got to grasp what is creating the incentives to generate a personal narrative. Fallout 3 apparently pulls it off, with many people praising the game while denouncing the main storyline. When do you ever hear about people praising the sidequests of a game? Contrast that to Far Cry 2, which I enjoy immensely but have to admit that you get stuck in a rut. AK-47, Grenade Launcher, and submachine gun have been my weapon stock for a while now. Obviously the games are working with very different game designs, but is that indicative of the FPS not working well as an immersive game or that RPG's are the best game designs for emergent narratives?
I ended up comparing this to the whole Gordian Knot problem with Alexander the Great. You can either solve the puzzle with the sword or by carefully solving the problem. The dilemma, both in the story and in games, is when the reward is the same for either solution.
The refreshing thing about Crayon Physics Deluxe is that it captures the essence of the problem these AAA titles are facing in a totally different setup. It's a physics puzzle game where you can do anything and as a consequence many players get stuck in a rut using the same tricks to solve every puzzle. They get to the end, feel a little hollow inside, and can only fool around without the same goal completion to get much out of the game. How do you get the player to use their freedom for something interesting without it feeling like work?
I'm not sure this has all the answers, but it's a start.