For the longest time I've been wondering why everyone seems to be clamoring to spend hundreds of dollars just so they can play The Elder Scrolls IV, and it wasn't until I played it that I finally figured out why: because it's worth it. Oblivion is one of the most beautiful and detailed games I've ever played, and it's extremely open-ended as well, making it almost impossible to complete the game 100%. As you travel through the vast overworld from area to area, you'll pass so many things to do that you'll find it very hard to just do the main quest. There are so many towns, forts, and caves to explore, so many enemies to battle, and so much to see. It really feels like a real, living, changing world. You can find encampments out in the wilderness, breathtaking lakes reflecting the amazing sunset, remnants of old forts and civilizations; there's just so much in this game. At one point I found a statue so beautiful that I actually stopped there and waited for the sunrise to get a better look at it, and I'm the kind of guy who will usually play just the main quest and ignore all else. Even with just your character you have an alarming number of options for customization. The smallest of details seem amazing with Oblivion's graphics, including something simple and everyday, like watching a cob of corn roll over in a bowl when you pick up the one next to it, and fallen foes' bodies fall against walls instead of through them. Every single bit of dialogue features excellent voice acting, aiding to immerse you in the experience.
I know I'm rambling here, but I've just recently played the game at my friend's house, and there's so much to love about it that I don't even know what to say. It is truly the most beautiful and detailed game of all time.