I'm surprised to see the love for Muppets Treasure Island, I really like the movie but had the impression that franchise purists weren't fans of the adaptation films (and based on its box office numbers audiences weren't too enthusiastic either). I also like that it was a world where Muppets and humans coexisted outside of the central characters.
I never followed the classic series and actually just started watching Season 1 on DVD. Everything feels good about it, especially from a mock variety show format. The show has a very positive energy to it.
I prefer Brian Henson's adaption movies to Manthann Tbh. The first Muppet movie and Caper are only equally solid movies in their list so far in my eyes.