The most beautiful RPG I've seen for both a great storyline and vast amounts of gorgeous scenery to wander around in and explore is Oblivion (the Elder Scrolls series of games). If you have a good enough graphics card it is simply gorgeous. You can even see every leaf on the trees moving in the wind. Weather effects are great. Sun and shadow are well done. Both night and day are beautiful to look upon in that game. Buildings are also very well done, as are the many game characters and animals.