These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: Pokémon: The First Movie
Animation Age Ghetto: Defied for the Japanese version, according to Word of God. Takeshi Shudo states that he made the movie to entertain children and their parents/guardians as well, and that he'd be "slightly embarassed" by parents who'd just take their children to see the movie as chaperones. It's a shame that, not only did 4Kids Entertainment dub this as a straight-up kids' film (as opposed to a family film), but later movies in the series would fall squarely into this trope.
Takeshi Shudo: Perhaps this anime is not only for children but also for their guardians: Where is this? Who am I? If you answer, "This is a movie theater where I seldom come. I am a parent who has a child. —Ah, child rearing is an expensive, tiring job," I'll be slightly embarrassed by your answer.
Anvilicious: Whether the film's aesop is "all life is equal" (Japanese version) or "killing/fighting (to the death) is wrong!" (English version), there's a scene with all the characters preaching about it from the sidelines.
The Japanese original qualifies too, seeing as it has a completely different soundtrack from the dub; the movie is full of appropriate and lovingly-written orchestral music, not to mention "Mesaze Pokémon Master", the opening song.
If you watch the Japanese version, try not to hear Masachika Ichimura as Mewtwo. Lots of fans had trouble adjusting to Reiko Takashima's performance as M16's "female" Mewtwo for this reason, with Dogasunote owner of the website Dogasu's Backpack noting that he kept lapsing into reading Newtwo's dialogue in Ichimura's voice when going through the M16 manga adaptation.
For the English version, this can either be subverted or played straight depending on your point of view, in that both Philip Bartlett and Dan Green seem to be equally well-remembered as Mewtwo's voice.
In the Japanese version, Mew is an even bigger victim of this, especially to people who grew up with the English dub. While it does side with Ash, it believe the originals to be superior to the clones and wants the clones to lose in a fight to the death. The problem is, due to Mew and Mewtwo being well-known as the hero and villain respectively, people are inclined to side with Mew despite the movie's moral of "all life is equal".
Ear Worm: "Vacation" by Vitamin C. Good luck getting it out of your head.
Ensemble Darkhorse: The movie played a huge role in making Mewtwo into this; he's well-loved by the fanbase both as a Pokémon species and as a character. This left many fans disappointed when the 16th movie would feature a Mewtwo, but not the same Mewtwo.
First Installment Wins: Most people know there were at least two movies, but most people (at least outside of Japan) don't know that there is a 15th movie, and counting.
Fridge Horror: What happened to all those trainers that didn't make it through the storm?
They might still be alive, due to Mewtwo pressing the Reset Button.
Growing the Beard: Specifically in Japanese, as the movie was the first Pokémon product to implement complex ideas and themes that would give older viewers something to appreciate and think about. While the English dub was much more simplistic, it at least kept the dark tone of the original, and many people still regard it as a step up from the regular episodes.
Ink Stain Adaptation: Outside of the fandom, the English dub of the movie is considered very shoddy, and is partly responsible for the anime's and the franchise's Snark Bait reputation in the West. This is especially bad considering that Shudo's original script is regarded as better than much of the series.
Jerkass Woobie: Mewtwo; while there's no denying that he's a dick, he had an incredibly tragic life up to the point where he vowed revenge on humanity. Even more so in the Japanese dub, where he just wants to prove himself worthy of his own existence.
Love It or Hate It: The English dub qualifies; some have fond memories of it and still enjoy how it took a darker turn from the TV series, while others dislike how watered-down and generic it was made from the Japanese version.
During the sad scene where all of the Pokemon are crying over Ash's body, the Dewgong start making sounds that are downright hilarious, especially in the Japanese version. Mood Whiplash at its finest.
Nightmare Fuel: Mewtwo. While Pokémon who are abused usually grow afraid or mistrustful towards humans, this one was driven half insane by it and decides to use his extremely powerful psychic abilities to exact his revenge, human and Pokémon alike. Given his game counterpart's ability in the later series to take on, and possibly even beat, other Legendaries, including Arceus, the god of all Pokémon itself, it's a very good thing for the universe in the animé that Mewtwo eventually decides to take a more productive approach to finding his purpose in life. The last thing Ash and his friends need is a Pokémon version of Kratos or Sephiroth running amok.
Subbing versus Dubbing: The dub is far more well-known in the Western fandom, and quite a few fans even ignore that the Japanese version exists. Despite this, people who can find the Japanese version tend to prefer it (thanks, Shudo). Though there are quite a few fans who don't like either version.
Vindicated by History: To some extent. The movie used to be on the IMDb Bottom 100 when it debuted, but now sits at an average rating. Most of the votes were initially from disgruntled adults taking their kids to see the movie, but they later became dominated by grown Pokéfans (the series' Popularity Polynomial definitely helped).
Easier (but not outright "easy") access to the original Japanese version of the movie also helped, as it motivated quite a few Pokémon fans who aren't too fond of 4Kids' dub to revisit the movie and develop a more positive opinion.
What Do You Mean, It's for Kids?: Many fans unfamiliar with the Japanese version tend to be rather surprised at the "meaning of life" themes, Mewtwo's greater complexity as a character, and the occasional mentions of God in relation to said themes. Which becomes Hilarious in Hindsight when you realize that now, there actually is a god in the Pokémon world.