As far as their original content, seems like Netflix has had the perfect combination of risk-taking, intelligent choices, and a bit of luck.
I read an interview with Kevin Spacey where he said after pitching House of Cards to all of the network and cable channels with lukewarm reception, Netflix jumped all over it. Not only that, when they said, "ok, we'll go film a pilot", Netflix said, "pilot? Forget that, here's $100M, go film a full season. Oh, and we won't mess with your creative vision, we trust you."
Just like more and more traditional "movie" actors are doing TV because HBO, Showtime, AMC, etc have allowed TV to be smart and edgy (and the filing schedules and promotions are mud mrs relaxed, etc), if you give producers and actors support and creative freedom they are going to start experimenting a lot more with streaming original content.
Then again, Netflix has basically stated they want to be the next HBO (and HBO is becoming a significant streaming service). Wouldn't be surprised if 5 years from now you couldn't tell the difference between the two - $10-15/mo subscriptions with a mix of original and licensed content...