Dawnguard >>>>> Knights of the Nine Hearthfire <<<<<<<<<<<< Oblvion Houses Dragonborn... doesn't really have anything comparable,* but it was still a damn fine DLC despite its flaws.
I enjoyed the Mehrune's Razor DLC well enough, but it was just a lengthy and uninspired dungeon crawl for one relic. Shivering Isles will be very hard to top for me, but it's possible that Skyrim might yet get a full-blown expansion under its belt, so the verdict will be out on that front for awhile.
On the whole, if I objectively had to pick between Oblivion and Skyrim's DLCs to decide which came closer to the definition of a 'scam,' I would have to say Oblivion's. But since I enjoyed both and don't cry myself to sleep at night over the two dollars I spent on Horse Armor, I can't say that I have any lasting complaints about either game's DLC. --- Simple questions deserve long-winded answers that no one will bother to read.