I'm most comfortable talking about movies on a narrative and writing level, because that's kind of where my competencies live, but any attempt to explain why Paranorman is so good demands that one range further afield, into areas where I'm not positive I really speak the language. But anyway: the cinematic craftwork, the animation, and the acting are all just really good. Impossibly good.
One thing that kept striking me both times I saw it was how well observed everything was. We had this back and forth outside the theater about real vs. better-than-real, and what I eventually decided was that the animation and design let the audience see the world the way a skilled artist sees it, giving us the illusion of a superhuman power of observation — not just including small details like the way a discarded flyer flutters against a cyclone fence, and not really forcing them on us either (like that fucking scene from American Beauty), but making it feel like we're discovering them ourselves and letting us feel kind of awesome for having done so. I think this is the thing I was grasping after when I was trying to talk about No Country For Old Men about four years back — not mere superhuman observation, but effectively showing you what it feels like to be a superhuman observer.
And in a related vein, I think the animation makes a more or less irrefutable argument for why one would bother with stop-motion in the age of CG. There were several shots where what should have been impossible was instead just brutally grindingly difficult.
Okay, anyway, I don't want to go on forever about the thing. But I do also want to mention how good the acting was and what a good actual horror story it was. About the latter, I think all I said last time was that the lightning witch at the end was legitimately scary, but thinking again, the whole situation is legitimately scary. This is kind of the big switcheroo vs. the movie as-advertised, and is partially obscured by the zombie slapstick, but the bones of the story are actually closest to The Ring, or maybe Stephen King at his rare best. The movie underneath the movie comes out in Norman's "How could you?!" and "They were men like you and they were scared and they did something unforgivable." And then it takes over the surface movie completely at the lightning witch sequence, as soon as we can hear what's left of Aggie's real voice. My point is, it's a familiar horror story, but we're coming at it from the wrong angle of approach and the real scary gets to hide underneath a fake scary for a while, and that's pretty cool.
As for the acting, I simply point to that awkward-but-chill back-and-forth between Norman and Neil about throwing the stick. And the lightning witch sequence, again, of course.