If you loved Pokémon Heroes, try Pokémon: Jirachi - Wish Maker
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
What they share
Both films are directed by Kunihiko Yuyama, and they both carry the cozy, playful mood tags, and they sit in Action / Adventure / Animation / Fantasy / Science Fiction territory. If that's the register that drew you to Pokémon Heroes, the second film will land in a comparable space — through a different lens.
cozyplayful
What Pokémon: Jirachi - Wish Maker is
Apparently someone wished for more Pokémon. Ash and friends attend a festival where Jirachi appears. It grants wishes, but probably not the kind its new friends had in mind.

