Nothing in any Pixar movie - not even the married sequence in Up - is as emotionally effective or devestating as the moment Simba lifts up Mufasa's paw and wraps it around himself. Original story or not. It's what they do with it.
This...that scene wrecked me every time I saw it as a kid (and I watched The Lion King like 14 times in 14 days when I first got the VHS...ah summer breaks as a 12 year old).
When I saw Lion King, I had just become a father a couple years before. My son, watching with me, was clueless about what was really going on, but emotionally I was a wreck watching that scene. I was yelling (silently) at myself: "It's a cartoon! You are crying at a cartoon!" But I couldn't help myself.
Since then, I've cried at many cartoons. Many of them were Pixar. I would want to go for Disney, if only for Lion King, and there are great parts of many of these movies. However, Pixar wins out overall, in my opinion.
Beauty and the Beast
Hunchback of Notre Dame
The Little Mermaid
Haven't seen all of Pocahontas. This is not to say that I don't think they are all excellent films. They all (except Little Mermaid) get 4 or 5 stars from me. But if we compare them like this...