I've had some experience with this, but generally, this is what I would do. If they are not experienced gamers, then don't worry about the system or rules, and don't let them worry about them. From what you're describing, you shouldn't be trying to find a system to fit the gamers, you need to train the gamers to the experience of Role Play and imagination. As others have stated, determine the setting of the game experience and then go from there.
For a fantasy setting, I'd recommend this: Get them around a table and start with having some of the core classes that exist in most any genre. Warriors, Thieves, Mages, Priests, etc. Have them describe their character to you, and everyone. What does she look like? What kind of weapon does he use? Give them the equipment. Don't bore them with costs, or availability, etc. Make sure the characters have healthy ability scores, so that the players can see their creation be successful in their roles. And just let them know, you'll be introducing more rules as time goes on.
Start with a small village, which can be made to appear in any setting, and don't focus on worlds, continents, countries, and the like. Start the group with the party knowing each other, perhaps growing up together, and then have them work on local items that are interesting. "Trying to find out who's poisoning the crops" might suck, but most everyone can envision combating the goblin menace!
Again, the idea would be to get the players invested in their characters, not a system. You might even just go with Basic D&D which is easily available as free-to-download "retro-clone" PDFs.
Part of what this is going to require is extra effort from you. When you are engaging them in the world, you have to be the catalyst for their role play interaction. Come up with three or four particular NPCs for them to interact with, and then you make the effort of creating their initial impressions with your own bit of acting. Say, there's an inn keeper in the village that they have to speak with. Ask them who's going to speak with him, and then physically act as if you are washing an imaginary cup when they begin to approach "him". "Evening folks, can I help you?" in a voice that indicates the change. Next be sure to require that their interactions are fruitful, without being painful. Don't require them to ask perfect questions to get results, have dialog prepared that gives them abundant info for modest efforts. Remember, again, you're not trying to teach them a game, you're teaching them the fun of acting in character.
Next, be sure that your initial adventures contain elements for each of the PCs to be successful. If you have a thief, have something locked or trapped (Again, something they can succeed with), if you have a priest, then some zombies to be blessed and turned, a wizard might have a few spells that are particularly useful. And don't ever start spellcasters in any setting with crummy spells. Give them useful spells.
If they aren't accustomed to role play, and you shove an 300 page handbook in front of them, it may be a negative effect. I would start basic, and just get them into it, and then make a decision on upgrading, or switching worlds, or even system's when appropriate.
Basic D&D is probably a safe bet, IMO, for a fantasy setting. The character sheets are simple, the rules aren't overly complicated, and it's easy to start. You can even adventure in worlds they might identify with. But really, the rules are irrelevant. It's the setting, and the characters that need to be interesting.
Remember one thing, if nothing else: the quickest way to get people incentivized to do something is to provide opportunity and results for success. If you start any game for new gamers, in any setting, be it mechanized, Star Wars, or fantasy, and immediately kill off two PCs, the effort is going to die.
So, to summarize:
- Healthy characters that fit something they want to play.
- Extra description and interaction from you, to incentivize.
- Focus on the gaming experience not the rules, and don't let them worry about the rules either.
My additional recommendations would be:
- Keep the introductory session brief (no more than a few hours)
- Have an introduction and a conclusion, and have rewards at the conclusion.
- An old trick I used to do was ignore experience, and at the end of a session, have the PCs go up a level. They get more hit points or life, they get new skills, etc.