FF9 and FF6 for me. I loved the look of FF9's locations. It was like seeing the games I had grown up with such as FF4, and FF6 in a 3D setting, and was absolutely wonderful. FF6 will also always be a favorite of mine. I loved places like the desert base, sealed gate, floating continent, Vector, Opera House, the Phantom train, Cyan's dreamworld, and I could probably go on forever. A lot of areas in that game are very memorable.

I've also got to agree with Prancing Mad on FF4. It had a lot of cool areas too.