Games

Pokemon: Black Ops 7

Whichever came out when you were in third grade

Personally I liked gen 6 a lot. X & Y feel a lot more mature than most others and I like that you have a friend group instead of just a buddy and a rival. Ruby & Sapphire were my favorites after Gold & Silver so alpha Sapphire and Omega Ruby hit the spot for me. Mega Evolutions are the best gimmick they’ve done so far IMO. I actually really enjoyed Pokemon Legends Z-A since it’s a direct continuation of the X & Y story. That said I’m not a serious Pokemon fan, I enjoy it sometimes and then go years without playing a mainline game.

I like the gen 3 games (R/S/E) even if they suffer from the damage type issue like someone else mentioned. Also HG/SS. I've been told B2/W2 is the one Pokemon iteration that actually has kind of a good story, but I never played those.

big fan of black2/white2, it's the last and most refined of the older 2D style games, the animated sprites look good and battle animations/HP bars/etc are nice and snappy, they respect your time. there's some fun gimmicks like 3v3 battles but they haven't started adding the once-per-battle supermoves yet, it's one of the "big" gens so you have a full blown roster of 150+ new mons with a bunch of old returning mons mixed in (YMMV on this last one, a lot of new stuff also means less familiar stuff)

Pokemon Mystery Dungeon 2 and Pokemon Conquest.

But for classic pokemon games Heart Gold and SS are really good remake, also Omega Ruby/AS, its mostly gen 2 and 3 but they are really good.

For the newest games ultra Sun and moon is one of the better ones and also pokemon black & white and its sequel black & white 2 are really good

heartgold/soulsilver are pretty good reimaginings/remakes of gen 2 if you want something kinda familiar

or firered/leafgreen for gen 1 but in the gen 3 engine

if your system can run switch games then scarlet/violet has problems, but is a pretty fun game in the newest pokemon formula

otherwise i would say maybe ultrasun/ultramoon for something new-ish with a different formula to the older games, though there is a lengthy tutorial which i personally found very annnoying

or my personal favorite is let's go eevee, but that is also on the switch

how much intuition do you expect to have retained? specifically, do you expect to have to learn type match ups and how stats work from roughly scratch?

supposing you don't have a strong feeling for which moves use the attack stat and which use the special attack stat, i would recommend Platinum as a good putting your feet back in. Emerald is also very beloved for good reasons.

to get aquainted with the modern series without straying to much from the OG game formula

in response to this, i offer a rough breakdown of the changing formulas across generations.

gens 1 - 5 have roughly the same feel: overhead view (with some partial exceptions in gen 5 games), sprite-based battles and animations, gimmicks are limited to new battle types.

gen 6&7: the 3ds era games, these switched to using 3d models for all the pokemon and the world, still a roughly bird's eye view of the world but without the strict movement grid to make use of the 3ds joysticks, and the introduction of battle gimmicks. gen 6 has mega evolutions which are an extra accessible evolution during a battle, somewhat divisive, but the most universally beloved gimmic. gen 7 still sort of had those but added in z-moves which were a once-a-battle overpowered attack.

gen 8&9: the switch era mainline games. behold, a conventional 3d camera view*. these started to experiment with less conventional battles. both of these generations completely excise mega evolutions and z-moves. gen 8 has "dynamaxing" which is a lot like mega evolutions but not limited to specific pokemon with a special hold item. gen 9 swapped the dynamaxxing during a battle for "terastallization" during a battle, which is swapping a pokemon's types for a different one, terms and conditions not withstanding. pokemon are on the overworld in both games. gen 9 has actual 3d movement in a meaningful way, gen 8 does not.

* well in the gen 8 games, there are routes like conventional games that have a fixed camera and there's a large open space called the wild area that has a conventional, 3rd person, player controllable camera. i personally found the wild area to be a very lazy and off-putting design.

https://pokemontoomanytypes.net/

Platinum or Heart Gold if you want something to play on your phone, X/Y if you’re using a 3DS emulator on a computer, Sword/Shield if Switch emulator.

Explanation of my answer because I’m high and felt like writing it out. I started playing Pokémon with Ruby and have played nearly every game since then, the only ones I’ve missed are Black/White 2 (2012), and Ultra Sun/Moon (2017). I have heard good things about both of those though.

Starting from gen 3: Ruby and Sapphire are obsolete because of Emerald. Emerald is very good, but it predates the “Physical/Special Split.” Prior to Diamond and Pearl, whether a move uses physical or special attack was determined by the move’s type, which sucked because it meant moves like Fire Punch wouldn’t use physical attack. This changes the games fundamentally and is a huge improvement. I love Emerald, but when I go back and replay it I use romhacks to implement the split.

Gen 4: Diamond and Pearl are obsolete because of Platinum. Platinum is a finalized version of D/P, it’s got a great story, and is reasonably challenging (for a children’s game). Cynthia, the champion, is generally remembered as one of the best battles in all of Pokémon. Heart Gold and Soul Silver are remakes of Gen 2 and are fantastic, and like Gen 2 they’re longer due to the Kanto second half. Obviously you know the story for those.

Gen 5: I liked Black and White a lot, it has one of the most memorable villains in Pokémon. I never played Black/White 2, but I hear they’re even better. My main reasons for suggesting Platinum over these are the champion fight and my personal preference.

Gen 6: X and Y are the first games on the 3DS, and the first games to introduce the Fairy Type. From here on each game has a battle gimmick, in this case it’s Mega Evolution. Certain Pokémon can Mega Evolve in a battle. Boosting their stats, giving them new abilities and sometimes changing their type. Mega Evolution is generally remembered as the best of the battle gimmicks. To be honest I don’t remember the story to these ones much, but I don’t remember disliking it.

Gen 7: Sun and Moon were the first Pokémon games I disliked, and the only one I played at the time and didn’t finish. I found the characters annoying, thought it was too easy, and at the time didn’t enjoy the changes to the Gym system. Also possible part of it is just that I was a moody teenager at the time. Ultra Sun and Moon are apparently significantly better and are very popular, but I haven’t played them so I can’t say. I believe Gen 7 also has the Mega Evolution system.

Gen 8: Sword and Shield are… okay. The better of the main Switch games, but I can’t say they were my favorite. Not a good challenge, I found most of the characters kind of annoying, although a couple of the gym leaders are pretty good. The gyms are mostly giant stadiums instead of small buildings, which is fun. The gimmick in these ones is called Dynamax/Gigantamax, Pokémon get real big because they wanted to show off what the Switch could do. It’s… fine. Not as fun as Mega Evolution. Legends Arceus is also considered a mainline game but it’s veeeery different, I highly enjoyed it though.

Gen 9: Scarlet and Violet are bad. They’re a buggy mess, they run like trash, they’re ugly as sin, they’re easy, they’re boring, and the characters are almost all insufferable.

the most authentic way to play pokemon is GBC gold/silver on a pc emulator with keyboard input

Gen 2 is my favorite Gen, and I'm long off the Pokémon train, with Black + White as the last titles I engaged with.

I loved Heart Gold and Soul Silver. They feel like the polished, finished versions of gen 2. Most of the gen 3/4 pokemon aren't really available until later on in the game, so it will probably feel very comfortable and familiar to you. At one point, I found a hack of HG/SS that upped the difficulty by making the AI stronger and smarter in ways that still felt natural to the game--e.g. gym leaders had a full team and used more healing items, sometimes x-items. It also added in ways to catch all the Pokémon to max the dex, which is really what I cared most about.

Honestly, the newer 3d games with hundreds more Pokémon and new battle/catching/evolution mechanics just don't look or feel like Pokémon to me, so I haven't tried them.

Heart Gold is the most recent one ive played cause I stopped at gen 2. It is absolutely stellar. Such a good game. It was nice being able to focus on catching up om the mechanics in a familiar setting with familiar guys cause a lot got figured out between Gen2 and 4. It's a fantastic time.

Another vote for Black/2/White/2 and HGSS. But I daresay I'd go Gen 5 over HGSS, it's absolutely goated.

Uranium?

I don't really like anything past Ruby, Sapphire and Emerald that much, personally. The last games that modernized a lot while still having the old charm would be Black & White, in my opinion.

Black 2. Gen 4 and Gen 5 was peak Pokémon.