Second place is a bit harder, but Platinum probably takes the spot. I said the games became steadily better with every new iteration with very few exceptions, and sadly DP was the prominent exception.
I would probably disagree with you there. I like Platinum, and it addressed a lot of the issues with DP, but it also retained a lot of the problems and I still think HGSS are far better games.
I won't let nostalgia dominate my view completely, though. I really believe Scarlet and Violet deserve to be up there with the best.
I will have to disagree more strongly with you for that one. SV had potential and they were better than SwSh, but even putting aside all of the bugs and graphical glitches, the games are still rife with problems and poor design decisions.
The open world was very empty and dull. Open spaces with Pokémon and items strewn about with little rhyme or reason. Towns no longer have buildings you can enter beyond gyms, which made them also feel empty and lifeless, other than slideshow NPCs juddering about the place. What do people do in those towns? How do they live their lives? We don't need Elder Scrolls's NPC schedules (though it would be nice) but at least let me see their shops and homes.
The game lacks level scaling, so the attempt at a non-linear story and gym progression fell flat when you are forced to either tackle them in the intended order or challenge higher level gyms for some semblance of a challenge, only to have to go back and mop up the lower levels later.
Furthermore, not only is the exp. share still mandatory, you are now forced to use set style battles. Game Freak seem so afraid of anyone struggling to complete the game's story, they have made battles utterly braindead. You don't need to train Pokémon, just have six in a party and you will end up with a leveled team. Sent out the wrong type? Don't worry, you will never be punished for it because the forced shift style means you have the option to switch.
I am genuinely afraid that they will implement auto-battle in the next game.
I don't understand why the game is set in a school, if after the intro you can drop that entire premise and never attend a class for the rest of the game. I think it was to reduce the amount of work done for player customisation and NPC designs by sticking everyone in the same four uniforms. Even adults, bafflingly.
Of course, dexit is still a thing. At least they gave us improved models and textures for the featured Pokémon this time. But I don't think many fans would be upset if they gave us the full Pokédex back but imported SwSh or 3DS models for older transfer-only Pokémon. At least they'd still be there and usable.
I too was very positive on SV when I first played it. I liked most of the characters and the story was serviceable. The open world was novel. But the more I played it the more the cracks started to show. Patches and updates made marginal improvements, but did little to fix the core issues.
My hot take is that Pokémon should never have gone 3D (or should have spun off the 2D games into a side-series) but I would rank SV on the lower end of the 3D games.