Unless you're flat out dead, you have to think of some other questions like: what's on the other side? It brings up issues of God, or no God. How does he play into this? Or he, or she, or it? How does it all play into this?
'Castle' isn't really affected emotionally by murder. He's thrilled about, 'Oh, my God, I wonder how this happened?'
The Polar Express is about faith, and the power of imagination to sustain faith. It's also about the desire to reside in a world where magic can happen, the kind of world we all believed in as children, but one that disappears as we grow older.