FFX, FFXIII and FFXIV. Easily those three. FFIX is full of what so many of the other games in the series lack: Fantasy. It actually feels like an "alien" world, which is something I feel strongly about with regards to fantasy. FFXIV has this in abundance too, especially with the expansion. I think the visuals we get in the expansion are second to none when it comes to being otherworldly. Upper and Eastern La Noscea are just beautiful, too. Pulse in FFXIII is incredible, too, with the unique take on your normally boring mine-dungeon (ie, it's carved out by a fal'Cie in a rather cool way).