Favorites:
The Spectacular Spider-Man: The best version of Spider-Man ever in my opinion and my favorite show of all time. Just, shows in general. I must've rewatched all 26 eps close to 15 times over the last 5 years. Best action scenes, drama, and jokes of any cartoon I've seen.
Any DCAU Show: I honestly can't decide between any of DC's animated shows from the 90's to the early 2000's. If I had to pick, it'd be between Batman: TAS and Batman Beyond, with Superman: TAS being right behind them.
Gravity Falls: Probably my favorite cartoon of this current decade. The mystery and animation was great, but the humor and characters is what made me stay. And it got a proper ending, which was amazing.
The Simpsons: Simpsons was a huge part of my childhood (I own season 1-12 on DVD). The newer seasons aren't great, but they aren't terrible. They just don't hit the marks as often as the 90's golden age.
Kim Possible: This is also one of my earliest memories and my only action show aside from Justice League. I've watched it recently and am glad to say to still holds up, for the most part (some of the lingo was way too early 2000's for me).
Batman: The Brave and the Bold: Probably the funniest superhero show of all time. And a great reminder of all the weird shit that happened during the Silver Age (what were they smoking?!)
Scooby Doo: Mystery Inc.: I'm mostly putting this one up because I've been seeing a lot of people put the original 60's show on least fav. I think this is a good reinterpretation and really funny (Fred steals the show with glorious trap obsession). The full series in on Netflix and I think you should at least give it a shot.
A Bunch of shows I like:
Futurama, South Park, Bob's Burgers, Powerpuff Girls Original (GOD, why do I have to add that now?), Rick and Morty, Adventure Time, Ed, Edd, & Eddy, Legend of Korra, Teen Titans., Jackie Chan Adventures.
Least Favorite:
Ultimate Spider-Man: With how great Marvel movies have been since the turn of the decade, it's a shame that they can't do animated shows for shit. Ultimate isn't terribly made (mostly, the animation can get really stiff, especially on supervillains), but it's leagues behind Spectacular. This show just straight up doesn't get the joy or drama of Spider-Man's world right. No one is in character, and it's just trying to be another Avengers cartoon. We have ENOUGH teams shows, Marvel! I want Spider-Man! Huge disappointment.
Seth McFarlence cartoons: Family Guy is trying to be offensive and failing, American Dad's characters are horrible, and Cleveland Show is straight up boring.
Mr. Pickles: Trying to be Family Guy but much worse. A clear sign that Adult Swim in general is just boring now aside from Robot Chicken reruns.
Johnny Test: The worst offender of rigs and WHIPCRACK! ever. Just horrible animation.
Most early Hanna-Barbara: It might be unfair to judge the comedy of the 50' and 60's compared to today, but most of them are boring and one-note. I respect some of them for what they helped to accomplish for animation, like Flintstones being the first on prime time, but anything before the mid-80's are just mediocre by today's standards.
Regular Show: This show is nowhere near the levels of bad of the ones I've just mentioned. It's well made and I could see why people might like it. I just found it very boring and stale compared to Adventure Time. I guess I'm just not into the whole "real life, suburban bro" type humor. Same goes for We Bear Bears.