Rotten Tomatoes is considered the most reliable movie rating website on the internet. It is a website that based on hundreds of reviews, it gets a percentage for the quality of a specific film. Their final rating its constructed in the following format "Out of one hundred critics, ____ said it was good, so therefore this movie gets a _%. After the major critical success that followed the release of Inside Out, Rotten Tomatoes gathered their best animated films and made a top 100 list. Their rankings were based on number of reviews and percentage. SURPRISE!! When I clicked on the list this morning, Inside Out was at the #1 spot with 255 reviews, and only 5 of them being negative. You can see the list below.
And can we also mention that there are 7 Pixar movies in the first top 10!!
EDIT: Now you may notice that amazing films like Beauty and the Beast and The Lion King aren't nearly as high as they should.. Well that is because after their re-release in 3D, some critics gave them negative reviews stating that the re-release was unnecessary, affecting the movie itself. Remember, Rotten Tomatoes is still relatively new, so movies that came out 30, 40, 50 years ago, don't have too many reviews, therefore diminishing the chances of them settling higher on the list.