This is a tough one for me, to be honest. It's an favorable opinion, but I think Up is arguably, if not their best film. I loved every second of it, from start to beginning. Up had the feeling that it was made with "love" and a lot of effort was put into it. Not to trash Pixar's other films of course. Don't get me wrong, Monsters Inc, the Toy Story Trilogy, and Finding Nemo. Pixar has great films such as Cars, The Incredibles, and A Bugs Life. They also had average at best, or "meh" tier films such as WALL-E, and Ratatouille. I haven't had the chance to see Brave or Cars 2 yet, and I'm looking forward to Monsters University and The Good Dinosaur (from reading upon it, it sounds great).
Sorry if this thread was created before.