I remember a time where cartoons were not joined-at-the-hip to their corporate overlords as they are now. A time when DIC was the name you'd see at the end of the credits of almost EVERY cartoon you'd see on Saturday mornings. Hell, a time where you would have a 6 hour block of cartoons running on just about every television channel.
(My family had a rabbit-ears TV when I was a kid)
I think the early '90s were the prime time for high-concept/weird-execution cartoons marketed mostly to kids. We were just getting out of the "half hour advertisement" era of He-Man, Transformers, Dino-Riders, M.A.S.K., Jayce & The Wheeled Warriors, The Centurions, Visionaries: Knights of the Magical Light, etc. Kids seemed to actually give a damn about the story, I don't remember if I did or not, but cartoon producers began greenlighting what I would consider more indie-comic ideas to become cartoons:
King Arthur and the Knights of Justice - A high school football team named The Knights, led by a quarterback named Arthur in "the present day", is pulled back in time by Merlin to rescue the real King Arthur and the knights of the round table from Morgana, who has trapped them in some crystal-thing, I don't remember exactly.
Pirates of Dark Water - On the alien world of Mer, a dangerous unknown substance, only referred to as "dark water" has begun consuming the planet. It's up to Ren, a prince, to try and gather the 13 treasures of rule, to banish the dark water. He must contend with Bloth, a pirate also looking for the treasures of rule, but he wants to use them to command the dark water, and take over the world.
Mighty Max - Based on a toy series designed to be a boy's version of Polly Pocket, but weirdly attempted to be educational as well; this series followed the adventures of Max, who has a magic dimensional-rift hat that takes him and two companions, a soldier named Norman and a scholar-bird named Virgil, Quantum Leap-style from place to place that needs fixin' by way of sword and wit. Probably one of the most inappropriate castings for Rob Paulsen, in my opinion.
Bucky O'Hare and the Toad Wars - A Space-faring green rabbit & crew are fighting evil, space-faring toads.
Cadillacs & Dinosaurs - In the future, mankind has developed a ruinous relationship with nature, and dinosaurs have come to walk the earth again. A group of grease-monkeys form a rebellion against a tyrannical government.
Eek! The Cat - Eek is a purple cat who loves to help people, often putting himself in grave danger in the process.
Corollary: The Terrible Thunderlizards - Three dinosaur mercenaries are released from prison and given a mission to kill two primitive humans after the dinosaur scientists determine that if allowed to propagate, the humans will quickly take over the world.
Wild West C.O.W.-Boys of Moo Mesa - Anthropomorphic cows in the Old West
Biker Mice From Mars - A trio of anthropomorphic martian mice, who ride motorcycles, come to future-earth to escape hostile alien takeover of Mars.
Street Sharks - Four brothers are genetically transformed into anthropomorphic sharks, rip-off of Teenage Mutant Ninja Turtles.
Captain Planet & The Planeteers - I don't think I need a synopsis for this one...
The Ren & Stimpy Show - Again, I don't think I need a synopsis.
And those are just the weekend shows I remember; when Warner Brothers decided to set up a television broadcasting station they got themselves a 2-hour block of cartoons from Steven Spielberg, many of which have been mentioned here. Freakazoid! The Animaniacs, Tiny Toon Adventures, etc. There's one more I remember seeing the pilot of: the dogs of several national leaders are called to a secret base and put on suits to turn into anthropomorphic super heroes. Wikipedia and Google are failing me, so I can't find the name of the show.
Disney also had a good after-school block of shows: The Gummi Bears, Duck Tales, Chip & Dale: Rescue Rangers, Darkwing Duck, and others I didn't get into like Bonkers, Goof Troop.
Now, I'm trying to restrict myself to the early half of the 1990s, 1990-1995, because I think that shortly after that, pressure began mounting to make children's cartoons more "safe", where we get less high-concept adventure, and more zaniness and stupid humor.
While the production values and art styles varied greatly across series, I still believe these to be the halcyon days of cartoons, where people were allowed to take more risks with new IPs and still get them through production.
I feel that nowadays, even in the last 15 years, cartoons (along with most everything) are designed by committee and focus groups, intended to be marketed to the widest possible audience in order to generate a greater return sooner than a niche-market product would.