Gen 5, pretty easily. It was the only time theyve ever tried to make a new game instead of iterating on old ideas. The story is about as good as you can get for a pokemon game too

Gen 3. It felt like such a huge leap at the time going from gameboy color to the advanced plus we got the addition of abilities. The region felt very comfortable and I like pretty much every design.There being “too much water” was actually a plus for me since I love water Pokemon. I still miss diving to an extent since even though there were essentially just routes gated by an HM. Contests and Bases also were a great addition. Contests adding a different type of challenge to pursue was welcomed even though they were not the most difficult thing in the world. Bases really added that element of going off with your friend to make a fort in the woods and the fact you could have one of your friends bases that you could visit and challenge was fantastic (also a nice little xp/money boost each day)

It was fun to run through again in ORAS as well with the added benefits of including mega evolutions so Gen 6 is a close second for me partially for that reason.

The first gen will anyways be best for me. Nothing else since had captured the magic I felt for that game with the exception of gen 2. Going through all of Johto and beating the game and then end up back in Kanto and beating that one too. That was truly special.

Other than Gens III and IV for pure nostalgia factors being the first games I played and whatnot (and HGSS being fucking amazing) I’d give a huge shoutout to Gen IX. It’s the first generation where I actually felt that magic that made Pokémon click with me so long ago.

If bugs and performance issues can ruin the experience for you, they’re definitely not recommended, but I don’t mind that much, and in terms of story, music, gameplay and exploration, I think Scarlet and Violet are possibly the best games in the series. They would’ve been perfect if gym leaders and titans scaled with the level of your Pokémon party, though then again, it was also very fun running around wherever and actually losing to them because you went to a town you weren’t supposed to yet. I enjoyed how little hand-holding there was in terms of story and progression, and that was awesome.

Overall that Gen was such a massive step up from gens VI-VIII, I can’t help but love it.

Mechanics wise, gen 4. The physical special split was one of the best things to ever happen to pokemon.

Games wise i’d say gen 5 unova is such a cool region and I love all of the pokemon there, although new pokemon wise I prefer gen 3

As incredibly flawed as Scarlet and Violet are, they make Gen 9 really compelling for me. Love the new Pokemon, playing through with a friend in multiplayer was a blast and being able to have my Pokemon walk with me is great. It’s an unfinished and laggy game but I haven’t had so much fun in Pokemon since Gen 5. Completely get why not everybody likes it, but I’ve had so much enjoyment from it.

As for Gen 7? I agree. USUM’s only major flaws are linearity (which I would argue was mainly bad for replays but fine overall), and that it removed what made SUMO so nice on its story. Ultra Beasts remain my favorite idea the series has done and the games had all Gen 1-7 mons plus megas plus Z Moves and the music was amazing and Battle Royale is my favorite multiplayer mode. Massively underrated, will be popular in three years when everybody suddenly loves it because old thing good, new thing bad. Mimikyu’s amazing.

Subjectively, I love Hoenn. It has that feeling of being at home when I’m there (especially the originals).

Otherwise, I loved HGSS, they really made the originals shine.

I was bored playing SUMO. Had to stop for a year before taking it back again, like XY. Not enough exploration. That being said, I miss this region. Alola had a slightly different feeling than all the other region. Something chill, made me feel being on vacation, ahah.

SWSH was pretty bland. I managed to finish it without dropping it but I never bother returning to it after the story ended. In the end, I sold it. I never sold a Pokemon game before, knowing that I have each generation physically.

Legends Arceus was great. Weak technically, but it was so fresh and fun. That’s the first time since a long time that I want to complete the Dex.

I’m waiting for the price of Violet to drop before giving it a shot.

EDIT : I didn’t mention BW and BW2. I really loved the idea of not having pre-gen 5 Pokemons until endgame. It helped to have a better feeling of discovery and freshness.

Gen IV, solely because of HGSS. Gen II holds a special place in my heart. Gen I is were I started, but I found Gen II to be everything I ever wanted in a game. Until HGSS changed that by making it almost perfect.

Honorable mentions: I’ve really like gen XI because of all the quality of life changes, the story was surprisingly emotional (not great, but better than any other gens as far as I’m concerned), and the terastilization is cool as hell. It genuinly changes up how I plan my teams and I get to experiment with Pokemon I don’t usually like or that have types that ruin them. Gen VI was dope too. Megas were awesome and ORAS is the definitive way to experience gen III.

Edit: Also, Gen VIII because legends Arceus was refreshing as heck. Genuinly made meaningful changes for the better and felt good to play. Despite being a much more limited experience. It was focused and fun. Probably my second favorite Pokemon game. SHSW were pretty weak, all things considered, but Legends Arceus was special.

Not a gen per se, but Legends Arceus was a Pokémon game that I immensely enjoyed. I’ve been playing since red/blue and over the course of the last few years, the mainline games felt progressively more stale and bland to me. Sword was the last main game I bought and I won’t be buying Scarlet/Violet - I’m put off by the hidden extra fees and have lost interest in the same age-old formula of “gonna catch them all” long ago, but Legends Arceus was different enough to feel “fresh” again, with a lot more freedom of exploration, direct interaction with your Pokémon and the environment and some interesting gameplay mechanics like being able to catch wild Pokémon without fights or lure them with food (think of Safari Zone, but 3D and with all Pokémon on the same map, no extra battle screen).

The only thing that annoyed me a bit was that the dialogue was dumbed down to zero, everything important was repeated around six times per conversation and you weren’t allowed to just skip it. That however is also an issue for the mainline games IMHO, so it was to be expected.