Both Skyrim and Oblivion are excellent games which have their own merits, but neither are perfect by any means. Both have certain things that they do better than the other. For example, in my opinion the atmosphere in Oblivion is miles ahead of Skyrim. The lush, green environment of Oblivion paired with its relaxing soundtrack make exploring the land an enchanting experience. However, traversing Skyrim's landscape feels more like a chore given the bland color palette and mostly rocky areas. While the combat is more fluid and fun in Skyrim, I prefer the leveling system in Oblivion more. And while Skyrim's main story might be more epic, the side quests in Oblivion are far more interesting.
Overall, I like Oblivion more, but Skyrim is just as good in its own way