If you loved Legend of the Millennium Dragon, try Pretty Cure All Stars DX2: The Light of Hope - Protect the Rainbow Jewel!
A bridge between a film you've already seen and one most people haven't. Pretty Cure All Stars DX2: The Light of Hope - Protect the Rainbow Jewel! has roughly 5.3× fewer votes than Legend of the Millennium Dragon — it's a deeper cut, not a mainstream recommendation. Here's what they share, and what the second one does that the first one doesn't.

Legend of the Millennium Dragon

Pretty Cure All Stars DX2: The Light of Hope - Protect the Rainbow Jewel!
What they share
Theysit in Adventure / Animation / Fantasy territory. If that's the register that drew you to Legend of the Millennium Dragon, the second film will land in a comparable space — through a different lens.
What Pretty Cure All Stars DX2: The Light of Hope - Protect the Rainbow Jewel! is
Here's a film that really wants to assemble every magical girl ever. When a dark entity seeks a gem holding all the world's hopes, it's up to the Pretty Cures to stop him. It probably pleased its target audience, at least.