I was never a fan of Wonderland myself, the world AND the film. I'll give my vote to it. 

Say what you will about Atlantica (And believe me, it's bad in both games), but I've never had an eye-rolling/sigh inducing experience like I did during Agrabah. The area just feels so bland with the sandy textures and lack of real shading outside of the Cave of Wonders. And, don't get me started on the fire versions of the heavy enemies. They're way to fast to spin around and block your attacks at that level. Plus, they have the homing Fira attack to take your health down quickly and most annoyingly. In all honesty, the level would be much better in my book if they'd just keep those enemies out of the whole dang level.

The Keyblade Graveyard. Any Disney option is more visually interesting than a dustbowl.

I was never fond of Atlantica (well obviously LOL). Regardless how beautiful it would look in the new engine, that singing game was the final nail in the coffin that killed the love for the gameplay in Atlantica LOL

I'll probably get flack for this, but Atlantis. I love underwater locales, like, a lot, but I just wasn't big on the movie. I'd much rather see a Pirates inspired water world.

Wonderland. I don't think there is anything left there for us (gameplay and story wise). I could always see us returning to Agrabah and Atalntica because they have more story in their film sequels (Aladdin 3 and The Little Mermaid 2).

Honestly, I really don't have a problem when it comes to worlds in the Kingdom Hearts series! If there's one in particular I'm not really a fan of, it still doesn't bother me. So really, I wouldn't be bothered when it comes to what worlds would return that we've already been to, ya know?

Frozen. Not because I didn't LIKE Frozen, I did, but because of the bad rap it would give the game for buying into what was famous at the time.

Wonderland. There is really nothing left for them to go over.

Star Wars and Marvel (MCU films). I rather have Frozen and Altanica in KH3 than Star Wars and Marvel.

Anything from Disney Channel

I really don't want to see or hear anything from Monstro and its world theme

No Monstro, no Star Wars, and for light's sake, NO ATLANTICA.

After playing khux na until the actual quest i must say that if agrabah is in kh3 then i'm probably going to have vietnam flashbacks