I'm watching Shrek on Cartoon Network, and aside from the editing of Shrek calling Donkey a jack-ass pissing me off, I was surprised by how poorly the animating has aged. I remember a documentary about the production, where an animator talked about how everything they were using was cutting edge. He chuckled as admitting that it would all be totally out-of-date before the movie even released.
Comparing this to the documentary on Pixar where in the early days of the company, they were desperate to find a real animator to bring life to all of their math. That's how they hooked up with John Lasseter. The amazing way that the animation of Toy Story 2 and A Bug's Life has aged, even as ever-greater advances in technology have rendered (pun not intended) the old technology nearly antediluvian, is hugely impressive. It shows how the fundamentals of animation hold up and remain contemporary regardless of when they're done.
For a direct comparison, look at the animation of Monsters Inc. and Shrek. They both came out in 2001 and likely had similar development cycles. I've posted a clip of Monsters Inc., which won't likely be up for much longer, and the trailer for Shrek. Just look at how much more flexible the Pixar characters are. Look at how much more fluid the movements are. The differences are stark.
By Shrek 2, the Dreakworks guys had either hired better animators or gotten the hang of squeezing character out of their more rigid model designs.