My top recommendations:
- Avatar:The Last Airbender: Don't be fooled by the fact that it's a cartoon and initially seems like it's just a kid's show. The show just gets darker and darker as it goes on. In a matter of days it went from something he was reluctant to try to the all-time favorite cartoon of The Nostalgia Critic.
- The Legend Of Korra: The sequel series to The Last Airbender. Even darker. Just as good.
TLoK is all about trying to maintain a fragile peace earned after 100 years of war, the threat of civil war, rebellion, terrorism, government corruption, betrayal...and even darker stuff that would be spoilers.
I honestly don't know that I could justify calling it a kids show in any sense.
I'd say it's easily darker than even Batman:The Animated Series was.
- Arrow - Easily the best thing that DC Comics has done since The Dark Knight. It's a TV show about the Green Arrow...vaguely like Smallville, except that it would fit in perfectly with Nolan's Batman universe (roughly 100000x better than Smallville).
- Supernatural - All the world's legends, myths, folk tales, ghost stories, and horror stories are true. Two brothers travel around hunting them, saving people...and their problems and situations keep escalating to the point where these two guys are basically the embodiment of "you can't imagine the things that I've seen and done".
Yes, it's as grim as it sounds...but it's also funny as hell.
- Better Off Ted - Ted is the head of R&D for a massive soulless and/or evil corporation. He's in charge of the super scientists who invent all of the company's batshit crazy products.
This show was funny as fuck.
- Veronica Mars - Before the show even starts, Veronica's best friend is murdered, her father(the town sheriff)'s suspicions/accusations of who did it cause her family to become outcasts in the town of rich people. Her mother leaves them, her rich friends turn against her, her father loses his position as sheriff. Her father opens a detective agency, and Veronica becomes his "assistant". Veronica is as good or better than her father, and she has begun to unleash her wrath on the town full of asshole rich people in her quest to find out the truth of who murdered her best friend. She wages a one-girl war for justice on all manner of fucked up shit going on in her town.
- The Venture Bros - I don't even really know how to describe this show. It started out as more or less a parody of Johnny Quest and other Saturday morning cartoons if they were subject to the realities of a slightly more realistic world....and it just kept getting more and more and more and more and more and more complex and clever.
It is, bar none, the cleverest show on TV.
The more pop-culture you're familiar with, the more of the references you'll get. It's an elaborate and densely woven tapestry of references like no other.
And that's just the superficial stuff.
The show is awesome and hilarious and full of references, but it also becomes an extremely in-depth deconstruction of the psychologies of the show's characters and their archetypes.
(The ONLY downside is that the show only has 2 writers -Doc Hammer and Jackson Publick- and, as a result, it gets to be SUPER well written, but also takes AGES to make. That's why it's been running for 10 years and only has 5 seasons so far.)