True, but I am not going to be awed any more or less, it will just be more or less memorable to me.
Sure the grand canyon was amazing, but that grouchy bastard sucked. This is probably what is coloring some opinion of the movie. I am saying objectively, If I were to be shown 2 scenes of amazing 3D-ness, the amount that I am awed will have nothing to do with the story.
Lets take the 2 scenes. The HTTYD scene first. Did I enjoy this movie more? Yes. Was that scene better? Yes. Did it awe me as much? No.
It probably has to do with how realistic the scenes were. Where on pandora you saw regular dudes walking around, you could imagine yourself in that environment. In HTTYD as beautiful as that setting was, it was a cartoon, so it didn't pull me in as much. (I would actually say that the vistas in Cars actually wowed me more) I think that people's dislike of the story in Avatar is coloring their opinions. (which is just weird to me) The way that Avatar was set up, specifically made you feel that you yourself could become a blue cat man and ride on these creatures. That you could experience this first hand. HTTYD was just touching. (And definitely got a bigger emotional response out of me)
But I think of emotional response to characters and emotional response to the CG as different things. At least in my mind. When I am awed by some scenery I generally don't think of the context, because it doesn't matter. Who cares who designed the "House on the Rock" (Frank Lloyd Wright) the place is amazing, and no matter who I visit it with, it is still going to awe me.
Now, if I were to suppose propose to my wife there, or bring a child there for the first time, and see their eyes light up. I might think of that as my favorite place on earth. Though, If I were to go to the top of that giant tower in the UAE (I think, maybe it is Qatar?) I might think that is more breathtaking.
The Avatar scene probably wins out for me, at least in part because it was the first CG I ever saw of that quality. (You always remember your first time) It looked real, and I basically spent the entire movie pinching myself to make sure this wasn't all a dream. Visually that movie blew me away. (IGN.com) But, that is all I will probably remember of it, because it was a cookie cutter story. HTTYD however, will definitely be more memorable in my mind.