I don't see why you'd be upset to your stomach....how many of those films were Disney films? That's should be considered quite an accomplishment since probably 75+% of them are Disney.
Toy Story was selected #1 because it was truly innovative at the time. No one believed that computer animation could be done to support an entire feature length film at the time. It truly set the standard for all computer animated films that have come after it. The characters are truly amazing and the film really does tap into everything that children have always dreamed about: their toys being alive.
The only other film that I think should've fought for that top spot is Snow White, but in the end, this movie was nothing more than the first color animated feature and that's about it. There are at least 3 full length animated features that were developed before Snow White ever came out, but since they were created in Europe and Mexico they are normally overlooked.
Little Mermaid is also more important than the list shows. It kickstarted the animation revival of the late 80's/early 90's. Without Mermaid, Disney probably does not go on their string of blockbuster animated films.
Also, though I at times argue the point of importance, where is Roger Rabbit on this list? I think Nemo, the Incredibles, Toy Story 2 and Ratatoille should fall much lower on this list than they do. They weren't exactly groundbreaking films. They did have solid stories and great characters, but they weren't much more than the greatness Pixar had already shown us. I love Lion King as well, but I believe that it's a bit higher than it should be - Snow White, Little Mermaid and Iron Giant should all be higher on the list than they are in my opinion in regards to what they brought to the animation industry.