Peanuts was a gorgeous film because they went a more experimental route with the CGI. They gave it some sort of CGI + Traditional Animation + Craig Bartlett style top down stop motion (as opposed to 3-D stop motion with larger puppets) look to the film. And the end result was pretty unique and wonderful. It's a shame that they were only licensed to do that one movie and there's too much red tape to get another Peanuts story off the ground. But the film was able to condense the same Peanuts schtick into a good, working film, all while managing to make the ending happy and hopeful. I mean, how many Peanuts specials ended with either Charlie or another character ranting bout how regretful they are at the end? When the only wins Charlie Brown really got was the Valentines Day when he got a reused Valentine out of guilt and accepted it with gusto? They managed to make a happier, more fitting ending to Charlie Brown than the comics actually did, but without ruining the tone of the original series. A fantastic film.
But I do love me some experimental CGI animation. When we got the first batch of CGI films, you have to admit, they were pretty stiff. The Shrek films were made hyper realistic and kinda pastel looking for example. I have to say, if there's one film I'd credit towards changing the face of what CGI animation looked like, it's Madagascar. Now, I love the franchise for some reason, the Penguins and their spinoffs moreso. While I certainly won't call it the greatest CGI film taking away my bias, the film was the first (if not one of the first) to introduce squash and stretch into CGI animated movies. Something Sony pretty much specializes in now (I'll admit their films since Cloudy with a Chance of Meatballs are good looking). And I'd especially credit Pixar's The Incredibles in finding a magical way to stylize humans in CGI so they look quite good. And studios have been pretty much copying that style ever since.