I would recommend Ultra Sun & Ultra Moon, honestly. While the story is notoriously inferior to the original Sun & Moon due to the changes, I feel like they upped the challenge a bit which made the gameplay a bit more engaging. Additionally, there were more Ultra Beasts added, Ultra Wormholes, and the Team Rainbow Rocket post-game section. While the story in Sun & Moon is superior, I enjoyed Ultra Sun & Ultra Moon far more in terms of gameplay.
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The Switch games are kind of a mixed bag.
Let's Go, Pikachu! & Let's Go, Eevee!
Some people get enjoyment out of these games. I'm not one of them, so I can't say much. Capturing Pokémon is done like it is in GO and you only battle trainers. Having started back in 1996 when the series came to the US, I've been to Kanto enough by now and didn't really need to go again. They also have moves with goofy names for your partner Pikachu/Eevee like Baddy Bad, Freezy Frost, Splishy Splash and Zappy Zap and it just feels like this was targeted at 3 year olds.
Would I recommend them? Not personally, no, but someone who actually enjoys it and can give a fair assessment might give a better idea.
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Sword & Shield
When Sword & Shield released, I was pretty negative on them. You might have heard about Dexit, where starting with Sword & Shield, they would no longer have the National Pokédex and not all Pokémon available in the games; whereas in every game prior you'd been able to transfer in any Pokémon who weren't included in the main games' roster. This bothered a lot of people, myself included. This was remedied to a degree via updates to coincide with the DLC, but even still, there are some Pokémon you can't transfer in. Regardless, it's better than it was at launch.
As Alolan_Apples mentioned, the story is pretty underwhelming, so that doesn't help matters. Most of the characters are pretty forgettable and the true main villains of the game are the least interesting.
Even by Pokémon game standards the game is pretty easy and this is exacerbated by the fact that the Exp. Share is always on and you no longer have an option to turn it off, meaning all of the Pokémon on your team will earn experience (and EVs) when you defeat or capture Pokémon. Also, Game Freak is in the habit of having a new gimmick every generation (Gen 6 had Mega Evolution, Gen 7 had Z-Moves, etc.) and the gimmick for Sword & Shield is called Dynamaxing. Everyone's mileage will vary and people will feel differently about it due to personal preferences, but I personally find it the least engaging, laziest and most creatively bankrupt gimmick they've come up with so far.
Technical Machines/TMs have been mostly downgraded to moves that aren't so useful, while the better moves are now Technical Records/TRs, which are one use only and you'd need to get another copy of said move to teach it to any other members of your team.
All that said, it's not all bad. The clothing selection for your trainer is pretty nice, and if you care about that aspect, these would be the games you want to play as far as the Switch games are concerned; more clothing was also added to the games that you can buy after acquiring a Style Card you get as part of the Isle of Armor DLC. Also, while I don't like Dynamaxing on a creative level, the gym battles taking place in stadiums is admittedly pretty cool.
Would I recommend them? Tough to say. It has been years since I went through the main story, but the DLC seems okay and the trainer customization is appreciated. I'll loop back to it at the end of the post.
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Legends: Arceus
A departure from the traditional Pokémon formula, your character is transported back 150 years, before battles were commonplace and before Pokémon Leagues and gyms. In this game you're tasked with helping to fill up the first Pokédex within the Hisui region, which is Sinnoh before it became Sinnoh. You go about capturing Pokémon in various ways, whether it be throwing food to distract them, throwing items to disorient them, dodging their attacks, sneaking up on them or just weakening them through battle the old fashioned way.
There are some trainer battles, but it's not the main focus, especially since like I said it's before battling was commonplace.
There is actually trainer customization in this but, obviously, the fashion is from a different time period. Not bad for what's there, though the default hairstyle is the only longer hair for females, so there's that.
Would I recommend it? I absolutely love Legends: Arceus and definitely recommend it. Hopefully they make more games in this style in the future.
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Brilliant Diamond & Shining Pearl
Pretty much just the original games but with new graphics...though, outside of battles, the characters are little chibis and it's kind of a jarring design choice after we've had normal human proportions the past couple generations.
Would I recommend them? Maybe. Depends on how much you want the classic style of gameplay. I, for one, appreciate them for that. You can also get a free Mew if you have a Let's Go, Pikachu/Eevee game file on your Switch, and a free Jirachi if you have a Sword/Shield game file on your Switch. If so inclined, you can get multiples by putting them in HOME, deleting the save, restarting the game and getting back to Floraroma Town. So, hey, that's something.
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Scarlet & Violet
Finally, the most recent games. They are indeed pretty shoddily made, obviously developed under crunch conditions.
Trainer customization is mixed. Good customization for the face and hair, but the clothing is the weak spot. Since the story has you as a student of an academy, you only have four uniforms to choose from that are suited to Spring, Summer, Autumn, and Winter; purchasing the DLC gives you color variations of those uniforms but it's pretty unremarkable. You can change hats/headwear, glasses, gloves, backpack, socks/tights, shoes, and your Rotom Phone case. The Teal Mask and Indigo Disk DLCs add some new outfits and such, but it's all still kind of constrained compared to the previous games' options because they're all still basically uniforms.
Unfortunately, because of the crunch development, the tera raids are really finnicky and buggy, particularly at the highest difficulty level. The raids aren't so unstable that they'll, like, crash or anything, but there's a timer constantly ticking down that can be problematic because sometimes the game is apparently having a hard time managing all of the actions the players are taking. If it weren't so buggy it'd be pretty fun.
Despite all that, I really enjoy playing Scarlet & Violet. Paldea is a fun region to run around in, the characters and plot were better than they've been in a while, there's some cool music and the Terastalization gimmick is really nice in my opinion. The crystal "hats" are kind of dumb looking and they probably could've gotten the concept across visually in some better way, but the type-changing concept itself is solid and neat.
Would I recommend them? Let's say like 80/20 or 70/30 yes. I don't feel comfortable saying yes outright because the games obviously needed more time in the oven and stuff like high level tera raids actually irritate me. For what they are, though, I'd say they're enjoyable games and I lean mostly positive.
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To wrap things up, if you're into the collection aspect, getting at least Ultra Sun/Ultra Moon* , Sword/Shield, Legends: Arceus, and Scarlet/Violet might be something to consider because if you have a full Living Dex in Pokémon HOME, you can get a Poké Ball-colored Magearna. Not sure whether that's enticing to you or not, but figured I ought to mention it anyhow.
* With regards to Ultra Sun/Ultra Moon, the 3DS servers are shutting down this Spring. Pokémon Bank isn't shutting down just yet necessarily, but they did advise to transfer whatever you need to while you can just in case becuase they don't know when they will eventually shut it down. So, you'd need those Ultra Beasts you might not have.
As for order, I don't think it really matters.
(I played New Pokemon Snap, tho lol!)
