This is actually a pretty good movie, which has blessed it with a slight cult popularity. There's a good story here under the low budget costumes and family-friendly low-end PG rating.
The family-friendliness does makes it a bit childish - as in, fighting that's more slapstick than violent, some cheesy Aesop messages in the dialog, and some cliche elements - but it's a fun movie with surprisingly enjoyable storytelling.
The family at the core of the story is, to me, a big part of what keeps the movie grounded. The girls act very sisterly to each other, and show human fear and flaws, making them more real as well as allowing it to be easier to empathize with their situation. The father character is a little braver and more willing to go on his quest than he realistically should be, but as a father, he comes across as real. Believable characters is a massive plus in my book, as I'm a big "characters" person.
Which is good, because the plot is, to some extent, random. While there's a main quest - stopping the trolls - other things end up occurring along the way that detour this quest. Plus, each adventure is played up for full potential, moving at a pace slow enough to give the feel of the moment and let it linger a bit, which is the opposite of hyperactively-paced kids' movies which normally move too quickly to give enough time to even relate to what's going on. For example, one scene where the family ends up in Medusa's lair takes time to portray the daughters crying in fear and trying to avoid accidentally seeing Medusa (to avoid being Taken For Granite
), which stretches the scene out but also gives it more depth than if it were just a quick detour in the story.
The film's length allows the many plot twists to occur, while still moving at a pace relaxed enough to have plenty of character moments, and draw out each plot element to full drama. Thus, both the plot and the characters are brought to life in my eyes, like in a good book. The family and character moments are half of what make the movie for me, but the adventure and excitement are pretty good too. Reduced violence, but the actual plot twists are pretty good and affect the story very nicely.
Sure, the movie may be corny and low-budget, but if you can get into the right mindset, you can really enjoy the story and the characters.