It's tough to pick three but I'm going to try and pick a variety that stretch genres each that scratch a different itch.
Simpsons - Hard to argue w/ the longevity. I'd say this beats out South Park which I'd probably put just behind it in comedy/dark comedy. The Tick would be another comedy I'd rate highly.
Batman: The Animated Series - There are so many DC cartoons that I'd consider here but I guess I'll pick this one.
Scooby Doo: Just for nostalgic reasons. Could easily put Tom and Jerry or one of the Looney Tunes.
Going to leave out Anime entirely which IMO blow the doors off this category but if I had to:
Re:Zero, Death Note, Cowboy Bebop etc.