Final Fantasy III is an awesome game. It has a storyline so in depth that you will not walk away from it until the World of Ruin. Then, like me, you'll probably walk away several times.
The first half of the game has everything a perfect RPG needs HOWEVER the 2nd half is way too open. I found myself running back and forth to the walkthrough because I had no idea where to go next or what to do. Maybe I've just gotten too old and my attention span has been drastically drained, but it's an RPG (which is fun, but to be honest RPGs are slow enough without not knowing where to go next).
But anyways, buy this game. With the slight downfall in the second half, it is still an incredibly great game and will always be among my favorites.