I don't have a lot of respect for a lot of modern cartoons (sorry) but I've gotta say that Gravity Falls and Steven Universe are pretty great - Gravity Falls for its unique blend of whimsy and dark humor, and Steven Universe for its upbeat nature and drop-dead gorgeous art. I'm also a pretty big fan of the older Spongebob episodes, and I used to watch Danny Phantom pretty avidly. Oh, and I own every episode of Avatar the Last Airbender on DVD. BEAT THAT, NERDS.