It's very difficult to say, for me. I think it would be between any of the latest four additions to the main series.

FFX has some absolutely gorgeous settings. The pictures supplied by Chris do well to show just some of the many beautiful locations you saw in the story.

FFXI has variety galore, although I think it suffers slightly from having any stunning cutscenes with dramatic colouring/lighting which could have pushed it to the levels of the other three games mentioned in this post. I think single player games have an advantage in this area, however it remains to be seen if FFXIV can bridge that gap - I think it may just do it.

FFXII has the best of X & XI moulded together. The style of movement and battling coming and going in real time meant that it had to be expanded a lot which limited things, however there were some moments where I was blown away by the brilliance of what they'd put together. I thoroughly enjoyed the Giza Plains and how they changed over the seasons, something I think that should happen in all future FF games. There were deep jungles which were lovely, but the one thing that really won my heart was near the end of the game - the "edge of the world" where an entire ocean turned to a fantastic waterfall, and the tower at the top... it was just amazing. I have yet to see a location make me simply think "Wow." as much as that.

FFXIII's graphics meant that it was always going to be ahead of the rest when it comes to detail, but I think there was also an added bonus in having two contrasting worlds. Some of the scenery was beautiful, particularly on Pulse. I actually wish there were more cutscenes on Pulse, if only to show off the scenery like FFX did so well.

All things told, the individual location award for me goes to FFXII while the overall world award goes to FFX. Even though I didn't like the game so much, I adored the scenery.