There are a lot of great suggestions so far, like Dogs in the Vineyard, Prime Time Adventures, and so on. But these don't address one of the principle problems for first time indie gamers: ease of adoption. There was a kind of a paradigm that happened a few years ago when the indie scene took off. It was basically the idea that no-one had to do any preparation and that the story would emerge during the game, not before it. It was the idea that characters and stories were aimed at one another, that, in lots of cases, the story was built collaboratively, and that the game acted as a tool to help in that process. It was all this stuff, and more, and it was really, really hard for me to get my head around it at first.
When I started playing indie games, I had real difficulty understanding that paradigm mainly because the games I tried seemed to incorporate it as a silently acknowledged facet. That is, it felt to me that there was something that the authors all understood, but that they weren't explaining in their text. It was only after playing with other people who'd played it before, and after reading and listening to podcasts of APs, that I started to understand what was going on. In other words, I had to do a lot of homework before I 'got' the paradigm...if indeed I ever got it.
So, for that reason, I would suggest looking at games that deliver the instructions without any indie baggage or assumed knowledge:
A Taste For Murder by Graham Walmsley (simple rules, breaks the mold in a satisfying and digestible way, offers great gaming advice)
Hell 4 Leather by Joe Prince (highly structured, easy to follow, delivers a spectacle of hellish drama using tarot cards)
Contenders by Joe Prince (again, highly structured, builds intense drama, a real eye opener)
InSpectres by Jared Sorensen (loose and fast, quite funny, and a great tool to introduce players to the idea of narrative control)
Hell for Leather by me (highly structured, simplifies narrative jurisdiction, uses a tower of dice like jenga)
I've tried most of these on non-gamers or 'trad' gamers (except for A Taste for Murder). Without exception, they've all produced a "wow!" moment once the players understand that they are collaborating to build a story. Plus, they're all easy to read, interpret, and play.