Cinderella II and III weren't nearly as popular as Cinderella...does that mean Cinderella was a flop? The Little Mermaid has a 92% rotten Tomatoes score, but the Little Mermaid 2 got a 33% -- guess Little Mermaid was just a fad too.
Now I will ask - has there ever been a Disney Animated movie (other than Pixar movie) whose sequel was a big success? I certainly can't think of one, and looking on boxofficemojo, The Jungle Book 2 made the most money of any Disney Animated movie sequel (disregarding pixar) at $47,901,582. When I heard Frozen 2, I kind of expected it would be another film like this. I do think Frozen 2 will be more successful than any other sequel in the Disney Animated Universe (again disregarding Pixar), but nothing about it's success will be any indication of how successful Frozen is, or whether it is a classic. Obviously a few people will never accept the popularity of the film...just like many on here refuse to accept the popularity of Avatar (but I will agree Avatar will not have the same impact that Frozen will...but land will because of how immerse it will be, but the movie was such a big hit because it was a first of it's kind...Frozen just hit the public in a way that will always be around much like the Lion King).
But keep refusing to accept the popularity of Frozen and the impact it will have forever.