My girlfriend, who has a history with games, but not really much familiarity with RPGs wanted to try a final fantasy, since she knows i'm a fan of the series. So, i set her up on FF10.
I felt like the lack of an ATB system means she can take all the time she wants. The voice acting makes the game approachable. With the standard grid, you can't really make any mistakes in leveling. The story is sweet and sad and the characters are well written. The world is easy to navigate and you can't get lost. Most of the random encounters have a simple mechanic like Wakka beats flyers.
In short, i felt like if she only played one FF, 10 would encapsulate a pretty good example of the whole and doesn't really have landmines for people who don't have history with RPG type games.