And just what was it about that show that made it stand out from other Magical Girl animes? What was the key thing that made it different?
With Madoka, Urobuchi applied real-world morality to a child-centric fantasy genre in the same way Frank Miller applied real-world morality to the superhero genre in The Dark Knight Returns -- and he came out with a similar, cynical product. Urobuchi asks the question, "what would it be like if this concept existed in our world," and answers it by exploring the realistic emotional and physical ramifications of every trope the genre is built upon. In the world of Madoka, Magical Girls are stand-ins for child soldiers and child prostitutes -- naive children who are sold a beautiful fantasy in order to indenture them into a life of constant horror and exploitation. Madoka is the only time I've seen that (seemingly obvious) allegory applied to magical girls -- and the result is an incredibly unique series that explores a lot of new ground and has a lot to say about the sometimes terrible world we live in.
The series points out how exploitative, horrific, and abusive the whole notion of a magical girl would be in real life. It elaborates at length on how the genre is built upon the manipulation and exploitation of naive young girls who accept horrific and deadly responsibilities without an understanding of the fatal ramifications -- while being promised a fabulous fantasy existence that never materializes. And it does this while being a great representation of the genre it's actively criticizing -- which is no easy feat!
It has something to say about how we unfairly exploit youth/the next generation for our own selfish gain. In this allegory, Kyubey represents the adults (or the media) that sell fantasies to children in order to manipulate them into doing things that rob them of their childhoods.
Watching Madoka is the anime equivalent of watching fame crush once-innocent child actors like Lindsey Lohan, Amanda Bynes, and Miley Cyrus. These are women who transformed from angelic pop culture princesses into demonic, troubled "witches." They were sold fantasies where all their dreams would come true (fame), but the hidden price for the fantasy was sexual exploitation, dehumanizing commodification, drug addiction, and their very innocence. If you've watched Madoka, you can see that the series is not subtle about drawing the comparison between washed-out teen idols and magical girls.
The fact that it's about anything larger at all immediately sets it apart from other entries to the genre -- which tend to be sugary, meaningless wish-fulfillment fantasies for little girls.