> Angry Birds took the same game concept, added much cuter characters and art, and blew us out of the water with it.
Those were certainly factors, but don't underestimate Angry Birds' better controls and better interface.
I eventually gave Angry Birds a try, well past the initial hype, played the free version for a while and then bought the paid version to get more levels.
I then gave Crush the Castle a try. Yes, the characters and art were not as cute (although personally I actually prefer leaving crushed bloody corpses behind instead of merely displaced living pigs...), but it took me just a few minutes to completely forget about that. When playing either game, I'm not spending my time admiring the art...I'm looking at how the structure reacts to my shot and figuring out what I have to do next to complete the destruction.
What stopped me from buying CtC was aiming. Angry Birds uses a slingshot, so I can pretty easily set the angle of my shot. CtC uses a trebuchet where the player selects the release point after the trebuchet is in motion. Getting a specific angle becomes a test of figuring out the right release point, and then getting the timing right to tap at just the right time.
Worse, with Angry Birds I can zoom out if I want so that I can see the slingshot and the target at the same time, which helps in figuring out the angle I need and the force I need. With CtC, you cannot see the trebuchet and the castle at the same time. Making that even more annoying, when the shot is in flight the camera uses a close up on the shot so you cannot see the in flight shot and the castle at the same time. You don't see them together until near the time of impact. This makes it harder to decide what correction you need to your timing.
The result is that Angry Birds for me is the more cerebral game. I want to concentrate on the physics problem of determining the weaknesses of the structure and where to apply force and how much to achieve that. The gameplay does not get in the way of the structural physics game. With CtC, there is this annoying reaction time game (timing the release tap) that gets in the way of the physics puzzle at the castle, and the annoying camera adds needless difficulty, and so although I enjoyed it enough to play all the way through the free version, I did not open my wallet to continue.