I'll just add my two cents, as it it's a long time since I've been in a versus-fight, and I just can't contain myself any longer
Both are good games. But they are different games.
For me, the greatest difference is not that one game has spears and levitation and the other has not. It's the way they tell their stories. Morrowing svcked me in from the first second. The world was, in lack of a better word, developed. It made sense. Oblivion was more like "Huh?" With Oblivion's AI, voiceacting, quests and turns, it still felt like a dead world compared to Morrowind's wooden NPC's, walls of text and comparatively dull graphics.
Because Vaardenfell actually had some sociopolitical issues. It had trades. It had lore, regions and real borders. Oblivion had an economy based upon the import/export of cutlery, tongs and paintbrushes. And a dead emperor and a daedric invasion that no-one gave a rat's ass about.
Morrowind put the player in the center of the plot, and told it's story in a brilliant way, revealing details, half-truths and tidbits at excactly the right pace. Oblivion made the player a generic gopher, sent out on various suicidal missions for barely a "thanks" in return. I was half-expecting Jauffre to tell me to make him a cup of coffee at times.
Both games are still good. Head and shoulders above any else I've played. I like one better than the other, but I dare anyone to look me in the eye and say that one is the the greatest game ever made and the other a load of crap. They have more in common than not.
But one thing I'll say: the levelscaling in TESIV was really, really awful. A good idea, trying to keep the game challenging even at high levels. But terribly implemented..