Going to get shit on for this, but I always really liked 4Ever and Heroes, the setting in both those movies are just so beautiful and mesmerizing.
I just love that lush green forest in 4Ever and that town in the trees, I love Gen 2 Pokemon, and there were so many interactions with them in the movie. I will admit the story isn't the greatest, but it's incredibly comfy. I'm also a fag for time travel, so the twist at the end gets me every fucking time.
I like Heroes for pretty much the same reason, love the fucking city so much, the race at the beginning was cool as fuck, I remember being blown away by the feelings I had during one scene where Ash is just walking through a garden? It's such a minor scene, but it really drew me in as a kid.
Simply put, I really think it's mainly the setting in those movies that are the main contributing factors to why I like them so much, they're just so interesting and full of life, even if the stories are boring/generic, I guess I'm just fine with that as long as they take place in interesting places.
The first 3 are also very good, and Lucario is great too (again, mainly cause I like time travel shit) I don't really like any of the others to be perfectly honest, I didn't watch a lot of them until kind of recently, so maybe it's because there's no nostalgia? Not sure.