Given that the anime has run for over 20 years and counting, there is bound to be some aspects of the show that people have different opinions about.
- The series itself is very divisive among older fans, more so than other Pokémon incarnations. It's either an awesome cartoon that you grew up with, a Guilty Pleasure that's had its ups and downs, or an embarrassing Franchise Zombie that needs to be kept as far away from the games as possible. In this respect, it's considered the '90s equivalent of The Transformers and Teenage Mutant Ninja Turtles (1987), both of which have similarly divisive "were they good or was it all just nostalgia" reputations.
- A section of the fanbase is split on if the show's focus should be on highlighting and progressing Character Development with serious arcs and a strong narrative, or rather be on entertaining episodes with little regard for the larger picture. Fans of the former usually favor entries that highlight Ash's veteran trainer status and face him and his companions with problems to overcome in terms of rivalry or internal struggles, and feel the show should focus on portraying him as a skilled trainer and progress as a character, and tend to perceive entries where his skills and/or personality hit the Reset Button back to square one as going against what the show should be about; fans of the latter tend to favor episodic storytelling, a take on Ash that highlights his more amusing and/or Butt-Monkey sides, wacky plotlines and amusing interactions between the cast members over major plot beats, either being largely uninterested in development or finding the major plotlines of the show to be nothing remarkable on the whole or pointing out their futility if none of it is guaranteed to carry over to the next entry.
- The Dubbing versus Subbing debate exists and is a persistent debate. Originally, the fanbase was strictly on the side of the dubs; however, as the Japanese version became more popular due to it becoming easier to access for overseas audiences, the launch of Dogasu's Backpack and the change in dubbing companies, the quality of the English voices, music, and scripts became debated compared to the subs.
- The league. For over twenty years, fans and detractors of the anime have argued back and forth over this part of Ash's journey. Supporters, while annoyed at Ash's constant losses, defend its presence in the show's Story Arc and believe it is a vital part of Ash's journey, alongside a framework through which his progress can be measured, his rivalries be developed and concluded, and provide each regional adventure with a climax related to Ash's skill as a trainer. Detractors often point to how the anime's formula surrounds the league conference and thus causes the plot to feel formulaic and boring to them, alongside compounding the issues of Ash's continued role as the show's protagonist by making each new region's tournament a "Shaggy Dog" Story that he's fated not to win. Sun and Moon brought this to a head by either proving that the show would be better off removing this part of its formula, or displaying that it needs it to give the series direction and development, furthering the divide when the Alola League was announced and led to every character getting power-ups in the thirteen episodes preceding the League.
- Releasing Pokemon. Either it's a good way to keep the main cast from having Pokemon who could become too overpowered to make anything interesting or it wastes a perfectly good member of the team for seemingly no reason.
- The benching of all of Ash's Pokemon (except Pikachu) whenever he goes to a new region post-Johto. Those for it feel that it allows new Pokemon from other regions to get their chance to shine while also preventing Ash from becoming too strong with a team he's already built up. Those against it feel that benching them essentially writes them out of the show for good, especially post Battle Frontier, where Ash's older Pokemon are rarely seen apart from Charizard and Bulbasaur.
- Which series is canon? Ever since the BW series, the fanbase has debated whether a series is canon or not with the only series universally agreed upon being the OS to DP series. Many fans who believe BW and SM are not canon point to how tonally different they are with the former series going so far as to remove some of Ash's knowledge as a trainer to give a fresh feel to him. They also believe that XY was a return to the original universe and Ash's Unova journey was just an alternate universe. While SM had mistranslated tweets about the canonicity to serve as "evidence" for its status as an alternate universe. People who argue all series are canon point to the numerous references to past events and cameos by old characters, going so far as to say the people who deny events happen as not real fans of the show or telling them that they're trying to elevate their Fanon equal to canon. Those who argue that these series aren't canon say that similar events couldn't have happened in an alternate universe. Pokemon (2019) established that all series are canon by displaying achievements from all series, rendering the argument moot, but the debate manages to rock the fandom.
- Kanto: Considered good by some due to feeling fresh (before becoming a Franchise Zombie), with some good humor and an enjoyable cast chemistry, while to others it's seen as reeking of Early Installment Weirdness that's subject to Nostalgia Filter, and riddled with inconsistencies (both in itself and to the games) that later series avoided.
- Hoenn: Misty's departure and May's introduction served as this, as to some, Misty being replaced removed a vibrant cast member who was part of Ash's early core development, while others enjoyed having a new character with a more concrete goal, making her a Deuteragonist alongside Ash, and helped turn him into a mentor.
- Ash's lack of a rival is seen as either a positive as it allowed him to grow solely on his own and embrace a mentor role, or it detracted from the series by giving him no challenge outside of the Gyms and Battle Frontier.
- Sinnoh: The finale of the region either suffered from Arc Fatigue (with a 52 episode gap between the 7th and 8th badges), or was well-paced with enough interesting things that made up for the gap (6v6 between Ash and Paul, Team Galactic finale, Grand Festival).
- Dawn's Contest career was either a step up from May's, with more complex strategies and rules, or just a rehash of May's own arc that made Dawn live in her shadow. Furthered by the fact that they are the only two main characters to have the same goal in the series.
- While most agree that Chimchar had a strong plot and Character Development that tied into the rivalry between Ash and Paul, some feel this didn't justify him becoming a Spotlight-Stealing Squad note , while others believe that Chimchar's story justifies this status.
- Unova: The series can be seen as starting off strong with Team Rocket gaining newfound competence and importance along with a brisker pacing compared to the previous series, or is seen as the same with Ash gaining newfound ''in''competence, replacing previous, well-liked companions with a new cast entirely, and moving so fast that it resorted to an entire Filler Arc at the end.
- Team Plasma's arc was seen as either a passable villain arc that made up for the Unova League, or was a shadow of its game plot that had plenty of misfires and wasted arcs when it came to Charizard, N and Team Plasma's motivations.
- Kalos: While some see the series as strong thanks to Ash's newfound maturity, a Love Interest for Ash in the form of Serena, and a strong villain climax rife with Character Development, others believe that it came at the expense of making Ash into a Flat Character, had too much Ash Character Shilling, and that Showcases were a poor substitution for Contests that made Serena seem like a Satellite Love Interest.
- The Mega Evolution Specials were either a great side series that developed Alain and Mairin into characters in their own rights, irrespective of Ash, or were the reason that Team Flare didn't enter the series for the first 2/3 and thus weakening the villain arc.
- Alola: The radical art style change, shift to a stationary, school-based Slice of Life story and Ash's more expressive personality are seen as a breath of fresh air to the series to some, while to others it changes the series too much and removes what made Pokémon enjoyable in the first place due to no traveling and a lack of battles that had become the norm, and also has an art style that is at direct odds with all of the previous series.
- The stationary setting is seen as either a positive, giving Ash the ability to return to a fixed location after his adventures while allowing more recurring characters rather than just characters of the day, or it's a negative since it strips Ash of his wanderlust and removes one of the core components of the games and anime from the series, while giving a Compressed Adaptation of all other islands but Melemele.
- The upgraded animation is a major point of contention. It's either good because it makes every movement smooth or it's wasted potential by being used for expressions and funny faces instead of the battles where it's arguably most needed.
- The idea that Ash can transform his Electrium-Z into a Pikashunium-Z. Its either an Author's Saving Throw for those who wanted Ash's Pikachu to have his own Bond Phenomenon with Ash or a complete Ass Pull.
- Alain beating Ash at the Kalos League to become the Kalos League Champion. Those against it felt that after the far from insignificant amounts of buildup and the heavy hints toward Ash's possible victory that he should've lost to Ash. Those for it point out that Alain was a pretty strong trainer and that his Charizard, the one to beat Ash-Greninja, had already proven himself more than justified in his win, having gone toe to toe with many other strong opponents prior to the League (The fights with the Legendaries and the 10 consecutive Mega Evolution battles come to mind).
- The depiction of certain legendaries as "merely" very rare species and not lone individuals on par with gods. Either it makes complete sense as Legendaries are shown to breed, or it cheapens the awe of seeing them.
- Sun and Moon's approach of finally having several mythical Pokemon officially caught by (or at least allocated to) main characters. Some enjoy the taboo finally being broken and rare Pokemon being allowed in as main characters utilized by the protagonists. Others complain it takes away their elusiveness and makes them more generic. Then there are others who are merely split over the execution, particularly with so many given to trainers all at once, along with some of them barely doing anything afterwards in spite of their status (in particular Ash's Poipole until after the Alola League and Mallow's Shaymin though Ash's Melmetal was well received).
- Which is the better English Dub, TCPi or 4Kids? Those in support of TCPi cite their more accurate translations, none of the Bolderization that 4Kids was known for, and far less of a gap between the Japanese airings and the dubs (Before TCPi picked up the dubbing, it was a near year-long gap. As of Sun and Moon the gap is just over 4 months). Those in favor of 4Kids feel that they had better dialogue and a wittier script, especially with Team Rocket. Others point out that despite 4Kids known reputation for replacing the score, it was nowhere near as bad as TCPi got post Best Wishes, and their music at least carried some charm that TCPi's dub OST lacks. Then there are others who believe that 4Kids simply put more effort and love into their dub, something that TCPi's dub has never been able to recapture.