Let me introduce the 2 cardinal rules of making something for non-gamers:
1. What you like and want doesn't matter.
2. What they like and want does.
Hopefully there will be a connection between what you like and what they like, but when in doubt, they win.
Now, to break down the process:
1. Listen to non-gamers: listen to what they do for entertainment, listen to their complaints about entertainment (and not just, "it sucked" complaints, look for complaints about scheduling, organization, travel, and anything else peripheral to the entertainment experience). Look for a spot where a roleplaying game might be able to do something better than another medium. Include some non-storytelling mediums (e.g. social networking sites, fashion, etc.).
2. Do some market research: What sorts of stories do they watch, read, listen to and play? What genres? What themes? What brands (if you're going that route)? Where do they look for advertising about entertainment? This may involve checking statistics (tv ratings, book sales, etc.), doing focus groups, and all that jazz.
3. Make a roleplaying game that matches the stories they like and fits the constraints (and freedoms) of their lives.
4. Playtest with non-gamers who are your target audience. Let's face it. We gamers often try to steer rpgs towards what we're familiar with. We can check the math pretty well, but we're not the target audience. And "non-gamers" are not a target audience. You need to be more specific than that.
This is all pretty general, basic business practice, and it glosses over all the places where you can go wrong in the details. How to manage those details fills books, so do some reading, and talking to successful businesspeople often helps, too.