Final Fantasy XIII's PC port launched last month, however, the game's release on PC was accompanied by fans' complaints regarding the game's resolution, among other issues. Square Enix has listened to the players' feedback and it's currently working to give these options to players.
According to the game's Steam page, Final Fantasy XIII will receive an update in December that will "improve your experience on Steam." The update will add custom resolutions (720p, 1080p, etc) and graphic options.
Final Fantasy XIII-2, which will launch on the 11th of December, will also include these options. In addition, the game will also run at 60fps and include both English and Japanese voice options.