I don't know any other Pokémon games apart from Pokémon Go, Mystery Dungeon, and the core series. Personally, I enjoyed the two Mystery Dungeon games I played, and while Go isn't perfect, it was still quite enjoyable. I've only played a few of the core series games, so excuse me if I'm being ignorant. My least favourite Pokémon game would probably be Pokémon Yellow for me. I've never done a thorough playthrough on it, so I can't really judge it as much, but heck, I played it for a few minutes and already got bored. This is probably due to the fact that I did a FireRed playthrough before that, and the remakes were a lot better than the original graphics-wise. Another reason why I dislike this game is because of the fact that you can't get rid of or evolve your Pikachu, in which is a pretty bad Pokémon unevolved. There are plenty of other electric types that are superior to it. It's just a waste of space in your party.
Honestly? Pokémon Quest. I don't care for the art style, and I barely have any control over my Pokémon. At least in the Rumble spin-offs you had full control over the Pokémon in question. Second least... Maybe Pokémon Shuffle... and then maybe the first Pokémon Ranger for third, because it just seems impossible sometimes. Actually, maybe Dash fits here. I seem to remember it as bland.
The worst, most frustrating Pokémon game I have ever played is Pokémon Ranger, whichever one had Almia in the title. I have never been so frustrated with a game in my life, and haven't tried another Ranger game since.
Including spinoffs, Pokémon Conquest. It's the biggest pile of Pokémon-related garbage I've ever played. It's a below-average SRPG with an unappealing art style, a miserable attempt at a narrative, AWFUL music, and it has the audacity to use characters from the Samurai Warriors series...a series I am very fond of. I have played a lot of bad SRPGs in my time, but this one sits right at the top of the pile. They could have AT LEAST made it challenging, or added in some systems to set it apart from other SRPGs, but this plays like a badly-made Kemco RPG, just with a few Pokémon in it. Just THINKING about this game is upsetting. I'd rather play Gates to Infinity than this. It's that bad. Excluding spinoffs, Sun/Moon. It was like playing Black again, only with an even worse narrative and cast of characters...and I didn't think that was possible. Conquest might be the worst Pokémon game I've played, but Sun/Moon were definitely the most miserable, so they're not far behind. The thought that they could represent the future shape the franchise might take is enough to put me off ever playing another Pokémon game.
Out of all of the games that I've played I'd have to say Pokémon Pinball on the Gameboy. I just don't like pinball. Other than that probably Pokémon Conquest or Pokémon Go, both of which are boring spinoff games that don't really have much appeal to me, especially Go. I'm sure it's probably gotten better since I last played Go, but when it started it was basically Pokémon but without everything that made Pokémon fun.
I think Go is misleading the direction of both the franchise and the marketing behind it, so I really don't like it. Aside of that... Nearly every spinoff that isn't an old MD. Does the tcg count as a game, tho? 'Cause I really dislike how it is structured nowadays.
I'm gonna have to say either Black/White or D/P/Pt just because I can't remember any of the plot woops
I'd have to say the PMD games, I find them very boring nor did I really care for the story in any of the ones I've played, I couldn't even get myself to finish Explorers of Sky.
Pokémon go is my least favorite. I don’t care how many new updates there are, I can’t forgive it after it blew up in popularity in 2016. I just can’t. It bothered me so much to hear people talking about Pokémon, but they were all just talking about Go, not literally any other Pokémon game.
Diamond and Pearl. They're slow and have an atrocious regional Pokédex. Platinum fixes both of these problems and because of that, it’s one of my favorites.
I played PMD Blue Team a few years ago and got bored of it very quickly. So bored in fact that I haven't picked up a Mystery Dungeon game since and I have no desire to play one again. Pokémon GO is one of my least favourites too. I don't get the hype around it.
Sadly I haven't played some of the older spin-off games, mostly just played the core, MD, Conquest and Rangers, but out of all of them I would have to say Black/White, if only because I really didn't like most of the Pokémon designs for the gen. Other than that, I would have to say... the original Pokémon Red/Blue. As someone who plays games more for story than for anything else, story-wise Gen 1 was pretty bad, and I get why, but still; at least Yellow added a few things, but yeah, Gen 1 was kind of boring for me.