I loved seeing the modern films in KH3, but I was also very excited to see what could have been done with classic films like Aladdin or The Little Mermaid.
The reason why I think KH1 had the best world selection wasn't because the films were the most iconic, but because each world was unique (Coliseum, Jungle, Desert, Underwater, Graveyard, Pirate Ship), the design of each world was different and each world complimented the main story. KH2 came around and basically made every world a box with DISNEY worlds painted over it and the main plot wasn't really connected at all. KH3 finally came back to form, which is why I'm really hoping the trend continues in KH4.
Yes, I'm advocating for 2D films to be somewhat mandatory in KH games (at least do 2 per game - not counting 100 Acre Wood), but I guess I'm really just advocating for worlds that:
1. Are relevant to the main story
2. Are aesthetically pleasing (and different from the other worlds selected)