Not "clearly" superior to me, or a lot of other people. Origins took the best of AC's game play, created a beautiful Christmas atmosphere, crafted a terrific story, the boss battles are better, the female characters are not overly sexualized in their designs, and added some of it's own touches like the crime scene reconstruction.
Yes, it's not quite as polished as the other games, but the pros far out weigh the cons, and it's above the other Arkham games in quality, especially AK. Sometimes it takes a truly disappointing game to make people see how good they had it before. I suspect that is partially why Origins is a lot more appreciated now than it was on it's initial release.