Oblivion as an RPG is much better than Skyrim. Skyrim is a great game but it was so dumbed down and really wasn't very big at all.
Not only that but Oblivion's soundtrack is also better than Skyrim's. Skyrim's has absolutely nothing memorable for me other than the main theme. Tracks like Harvest Dawn and Dusk at the Market take me back to so many different moments in the game whereas I don't get that from any of the Skyrim tracks despite having played Skyrim for longer than Oblivion overall.
It aged terribly but overall Oblivion is just a way better game