I very much like Oblivion too, but I personally felt that something was "missing". First, I don't know much about the lore of the Tamriel & Morrowind, but I found the mounts to be incredibly generic & boring. Riding a mere horse just isn't very....interesting IMO. Well, there is unicorn, but that just a horse with a horn so its not very convincing. I'd wanted to have some type of flying creature, ridable lizard & other animals or at least something more original than horse.
Also the available "races" were a little less than original. Excluding the Argonians & Khajiit, they appeared to be just Humans & Elves with different abilities. Only Dwarves were missing...
The Argonians and Khajiit were basically the only ones I ever bothered to play, mainly because they were truly interesting and radically different from the rest.
Third little complaint comes from the very thin range of items and weapons, it's true that you enhance your weapons with spells & magic, but that just about it. Few classes of armor & Weapons just weren't enough for the game as huge as Oblivion.
Well, each shadow carries a light, or was it vice versa.
Some good points I found were a really wide and open world, well I would have wanted to see black march and other surrounding lands, but the game always turns me back. Also the massive amount of sidequests were sore to an eye. The graphics itself were, as expected, gorgeous and colorful. Well, I'm glad modding community is alive and well, and almost every day something new comes available. In all aspects the game still shines, despite its lack of originality and items. Many of the games problems can be and are solved by the modders, and as soon as my new ATI 1950 XTX arrives, I'll be giving it another try.
Sorry, didn't want this to sound like a mini-review, but I just wanted to write about the Oblivion's problems from my own point of view.