Final Fantasy VI is the last 2D Final Fantasy game, and the first one not set in a standard fantasy location (rather a steampunk one). The game's story focuses on a conflict between the Gestahlian Empire conquering the world, and the Returners, a rebel faction opposed to them. The Empire has acquired a great army through experiments with espers, magical demi-gods of legend. The Returners seek magical power to fight the Empire on equal terms, and an amnesiac former imperial soldier, Terra Branford, proves key to both sides for understanding magic and espers.
It's a considerably powerful installment, though ultimately below Final Fantasy V and Final Fantasy VIII, with several planet busting characters.