We enjoy in eminence
It's been a while since I've fallen for a TV show this hard. Steven Universe, now in its second season on the Cartoon Network, is wonderful. What's it about? Steven, a tubby kid with a pink gemstone where his belly-button should be, lives in a weird alien temple with three alien women, the Crystal Gems. They teleport around the globe, fighting monsters. Simple premise, right? What's so great about it?
Maturity
While it's ostensibly a kid's cartoon, the characters are mostly adults, and they have complicated grown-up histories and motivations, all presented so that kids can understand, but with their complexities visible to the adult viewer. Though there are other kids for Steven to interact with; his probably-going-to-be-a-girlfriend-eventually, Connie, is thoroughly realized, an awesome and totally believable little nerd-girl.
Intelligence
The back-story is rich and subtle- so subtle that I didn't realize until I browsed some fan pages that the show's setting is actually an alternate history. The writing is sophisticated- one recent episode had a fake-out plot spur leading to a reveal that (I noticed with a second viewing) had been foreshadowed at several points. A lot of the episodes are like that, with elements that reveal depths of characterization on second viewing, or minor details in the background that hint at things as yet unrevealed.
Beauty
And the artwork! Clean, distinctive character designs, lush background colors. I almost got distracted from the action in a recent episode just looking at the trees in the background. The characters often visit exotic-looking abandoned alien facilities (temples, combat arenas, laboratories, etc) and the art crew does a great job with the designs. It's worth scouring the backgrounds for implicit worldbuilding!
Music
The music is really great. One of the main characters is voiced by Grammy-winning singer-songwriter Estelle, and the characters often burst into song. Here's an example, an extended version of the show's theme song, shown at San Diego ComicCon this year. (Update: Here's the full version; it has a little extra conversation at the beginning.)
Diversity
The show presents us with characters from a variety of races, ethnicities, and body-types. Even the alien characters who make up the main cast don't all look like white people. A number of the characters (including Steven himself) are broader-then-average, and it's never presented as a problem, or as something to mock. If anything, largeness is associated with both power and beauty. (Though there are also skinny characters, and they, likewise, are treated with respect.)
Feminism
The Gems are (so far) all female. (Exactly what that means for a species that probably doesn't reproduce sexually, we don't yet know.) Not only that, but the show explores gender roles in a serious and intentional way, while still keeping things comprehensible for kids. There's even a multi-episode story arc revolving around sexual consent (handled at metaphoric arm's length).
I've had this sitting on my hard drive for over a month, waiting for me to figure out how to get more quotes from Paradise Lost into it ("Celestial rosy red, Love's proper hue"; "And these the gems of Heaven"; "And in the lowest deep a lower deep"), but eventually I gave up and went with this.