1. I think a nice open city/world, with plenty to do ala Gold Saucer in VII.
2. More than just one city. With towns, not just one shopkeeper, and at least one little stupid sidequest (jump-roping in IX come to mind) in each of them.
3. Inns would be nice. I felt like playing XIII and XIII-2 lasted the span of a couple of days for our heroes. Inns give you that sense of realism like weeks are passing as you beef yourself up.
4. A reasonable storyline.
5. A good ending.
6. A battle system that is intriguing and new.
7. Complete customization for Lightning (which includes whatever type of job you wish to make her).