The simplistic answers is: different taste.
The movies delve into the fantasy with pretty accurate and astonishing imagery. You get lost in the pretentious visuals. It's entertaining, it's beautiful, it's interesting, it's original, it's different, there are essential expressed human emotions people relate to and feel connected to, and all of it is on a high-budget, grand scale. Plus, there aren't many fantasy movies with such an epic storyline and visuals. If there are, then the management of that movie sucks at marketing! Most people don't go deeply searching for such extravagant fantasy films, but rather let the movie come to them, unless it's an extreme interest of theirs. Therefore, marketing plays a MASSIVE role in the popularity of a fantasy film too.
The movies you listed can't even compare because they aren't even apart of the same genre. Everything is different from the music, visuals, story, dialogue, time period in the movie, time period the movies were made, etc. LotR to Mary Poppins? Are you cuckoo for Cocoa Puffs!?
I liked both the LotR trilogy and The Hobbit for reasons I've previously stated. The overall grand elements of the movies made such a lasting impression on me that I qualify them as some of my favorites. Plus, they're the type of movies my whole family enjoys and will watch silently in unison together.
To my bewilderment, I don't see why some people label The Hobbit as "cheesy" or "childish." Perhaps they mean some of the early scenes in the movie, such as the singing-at-dinner scenes, but I didn't think it was that cheesy. In my perspective, it was a pretty realistic supplementation for entertainment, considering the time period that it's based off of. Moreover, it was only a brief moment of the entire movie. The rest of the film felt very Lord of the Ringsy to me. It was a bit less epic, but that's because the story was a bit less epic. It's a prequel TO the big shit. The suspense before the climax! The attainment of the drugs before the bust! The appetizer before the entree! THE BONER BEFORE THE ORGASM!