By unique I'm assuming you mean artifacts, and I'd rather they not spawn randomly. In Morrowind there were many hand-placed artifacts, Eleidon's Ward, the Dragonbone Cuirass, and the Daedric faces being a few examples, and for me at least, this added to the atmosphere of the game rather than if I'd found these items in a random chest. It gave the artifacts backstories that the player could only guess at. Other artifacts, and most -- if not all-- of the Oblivion artifacts were found through quests of the Daedric variety.
I have to agree with this. While I don't mind having unique artifacts in random loot in some sorts of games, such as say, Diablo, it's not really what I want from the Elder Scrolls. In such games, a lot of emphasis is put on killing lots of enemies in the hopes that you'll find some rare, powerful item, and that's not a criticism, because if I play that kind of game, chances are that's the kind of experience I'm looking for, but the Elder Scrolls, I feel, is more about exploration and quests, making these things feel rewarding and capturing the atmosphere of locations is important, and for this, I think some worthwhle hand-placed items is beneficial.
In any case, I don't see how randomly spawning makes unique items "truly unique", if anything, being hand placed makes them seem MORE unique, because you know that if you didn't explore this dungeon or do that quest, you'd never see that item, if they are part of random loot, you could potentially find them in any location that can spawn items such as them in the world. But really, when someone says "Truly unique items", I think of making the appearance or abilities of unique items more unique, and Oblivion mostly had the first one down, aside from the artifacts, many quest rewards looked different from normal items, at the very least they might have a different texture, in terms of abilities, though, while there were a few items with unique effects you wouldn't see anywhere else (Wabbajack, for example.) aside from the kind of boring but practical Azura's Star and Skeleton Key, most of these seemed like gimmick items for the most part, they might be fun to play with, but weren't actually extremely useful, and the other unique items tended to just have common enchantments, although artifacts were usually much more powerful than anything you could make yourself and most generic enchanted items.