Unlike Dr. A, I love Oblivion. The storyline is weak and the combat is too easy without mods, but Bethesda unlike Jowood, released tools to the public with the intention that people could change what they don't like about the game. Installing two mods made Oblivion a great game for me. After upgrading my graphics card recently, I downloaded some super high-res texture mods and have started exploring the game all over.
What Oblivion aces is exploration. The game is beautiful and there are a lot of things to find. I just love a game that has so many locations to discover. I'll admit that I'm an explorer at heart. I love finding all the ruins, shrines, dungeons, caves, etc. If you set the goal of uncovering the whole map, it'll take you over 300 hours.
Do the graphics get repetitive? Yep. If they had made unique graphics for all dungeons we wouldn't have seen the game until 2010.