It's in the eyes, I think. The eyes in this movie look a lot less creepy than they do in Polar Express, and I think it's because in Polar Express, you're looking at kids that, for all that they are in a fantastic setting, are supposed to look like regular kids. Using this kind of CGI to create larger-than-life heroes and supernatural creatures takes us away from the Uncanny Valley to an extent, I think, because we have no expectations about what, say, Grendel's Mom is "supposed" to look like. It's an interesting wrinkle to the Uncanny Valley effect that when you take otherwise creepy-real eyes and make them glow yellow, they are no longer creepy.