I could imagine that Oblivion would be somewhat boring after Skyrim. The world is relatively generic and the writing mostly boring (except for some quests). Not sure whether it brings anything to the table compared to Skyrim (which is considerably more gorgeous and a more interesting world, from what I've heard) and Morrowind, which has the advantage of being much weirder and non-generic in its setting. At its release, Oblivion had the advantage of being great to look at, but compared to Skyrim it won't have the same effect any more.