Television

Gravity Falls and Steven Universe are the first two to pop into my head. Both start out having pretty self contained episodes before opening up to a big story arc. I think Star Wars Rebels gets overlooked even though it has seems to have less filler than Clone Wars did.

My kids are no where near the target demo anymore, but we've watch all of Bluey as a family too. The number of times I've teared up at that show is ridiculous.

I'm also a fan of the Adventures of Pete and Pete, Rocko's Modern Life, Invader Zim, and Magus XLR but they all have a heavy dose of nostalgia for me too.

Avatar: The Last Airbender

The Owl House, for sure.

Also, Infinity Train comes to mind.

Steven Universe has a really special place in my heart it's really a show for all ages with the themes it grapples with in many episodes.

Adventure Time and Spongebob had a lot of stuff that only adults could catch. Also, a lot of shonen anime deal with mature subject matter.

My personal favourites are ATLA and The Owl House, I know they were already mentioned though.

Kipo and the Age of Wonderbeasts is goated with the sauce. Love the themes, the artstyle, the soundtrack, the characters... No joke, it made me cry on three occasions on my last watch (my 3rd). It's all even better when you're stoned.

She-ra and the Princesses of Power is really good. I like toxic yuri, and characters who just keep digging every time you think they've hit rock bottom.

Like others have pointed out, ATLA, Steven Universe, Infinity Train, Gravity Falls and The Owl House are all good, too.

Azumanga Dioh

The Sisters Grimm

Darkwing Duck

Gargoyles

Fraggle Rock

Phineas and Furb

Animaniacs

Just some off the top of my head that I have enjoyed rewatching recently

A couple not posted yet... Bluey, Foster's Home For Imaginary Friends

Invader Zim (obviously...)

Phineas and Ferb

Powerpuff girls

Avatar both Aang and Korra, easily some of the best characters and world building for a kids show

Zoids

Teen titans

Lot of the nickelodeon shows around early 2000s SpongeBob, fairy odd parents, jimmy neutron, Danny phantom. They kinda were releasing bangers for awhile

Adventure time I watched as an adult and really enjoyed it

PRODIGY is a good nutrek, unlike the 3 "live action ones", lower decks can be considered for teens? and good for adults. SGU wierdly try to target teens, but it failed poorly. young justice, some of the newer animated x-men spinoffs.

Can't believe no one's mentioned SpongeBob!

Dexter's Laboratory.

I did a rewatch of Avatar: the Last Airbender with my kids this summer leading up to the Magic the Gathering set, and I forgot how good it was.

The Dragon Prince is fantastic!

Adventure Time, Steven Universe, Star vs The Forces of Evil. Not sure how broadly we're defining "kids" here, these I guess might be more like pre-teen/teen/YA, idk.

Ren & Stimpy. Real talk.

Sid the Science Kid

Ulysses 31

Magic Schoolbus

Mighty Mouse: The new adventures

GI Joe PSAs

most DC and Marvel superhero cartoons.

ducktales original and 2017.

Just recently finally finished Adventure Time. The Fiona and Cake series on HBO is great (for adults though).

My toddler has become obsessed with Sonic the Hedgehog, but it's been hard to find any age appropriate stuff for him from that franchise. We recently discovered Sonic Boom, which is not only not too violent or scary for him, but is also legitimately funny. A nice surprise, since the only thing I knew about Boom was that the tie-in game was the worst Sonic game since Sonic '06.

I also love Star Trek: Prodigy
Other than that:
Avatar: The Last Air Bender
Star vs. The Forces of Evil

Been watching Sonic: Boom. It's great.

I haven't seen Bluey but I'm probably going to.

Also Adventure Time, Regular Show, Chowder, Gumball, and Gravity Falls also csme out when I was already an adult and I love those.

iCarly.

Both Avatar shows.

Oggy and the Cockroaches

Teen Titans Go

Going back aways, too, Blues Clues. Not that I still watch it, but when my kids were of that age, I enjoyed watching it, and I'd even watch it without them sometimes.

I'm going to shout-out Kids Next Door and Arthur. Loved both of them both as an adult and as a kid. Also, Recess.

I'm surprised that My Little Pony: Friendship is Magic hasn't been mentioned. For me it and ATLA are good for eternal rewatching.

Since ATLA was already posted (what a show, truly a pearl of Western animation), I'll say YuYu Hakusho. Yeah, it's a bit slow and repetitive but the emotional highs and lows still hit, and the animation and writing is still much better than much of what we have today. Also, seeing Yusuke's very real struggle (broken home, missing dad, alcoholic mom, feeling utterly pointless) still makes me feel strong feelings...

That nobody ever brings up Centaurworld is a crime.

Yall missed out on and still sleep on it.

Not including my top show ever despite being too old for it, Franklin ( that preschool show ablutnthe turtle ), I'm going with Summer Camp Island as maybe 2nd place right now since I started rewatching it again. 6 seasons of a show starting off fairly episodic before coming together to tell what I consider a beautiful ending, even if it kinda feels like they had a network rush placed on them. Absolutely LOVE the final episode.

Though I have also been rewatching Code Lyoko since they have a full dedicated channel to the English dub of the show on yt. One of my all time favorite kids sci-fi TV shows period. Giant foreheaded minors attending a boarding school and fighting a virus capable of doing impossible tasks like making teddy bears turn into giant monsters or take control of rats to cause a plague or something along those lines? What's not to love?

The Adventures of Pete & Pete

Totally Spies, The New Adventures of Winnie the Pooh, PPG, Courage The Cowardly Dog, Tom & Jerry, Flinstones, Looney Tunes, Masha and Bear, Larva, and many more.