While the dungeons are visually stunning and non repetitive they are completely linear with no exploration whatsoever. You go from A to B with zero side chambers/rooms to explore or walk past and get flanked. Or interesting places where the pc says "hmm how do I get up there"? So they replaced Oblivion's weakness of visually repetitive now they lack exploration and are too easy to get through. Dumbed down is an over used phrase on these forums but I think it fits in this case. At least in Oblivion you had to use your map to make sure you found every nook and cranny.

In a nutshell:
Skyrim:
Looks great
Is not repetitive
Too bright making torches and light spells/staves useless
Loot way too easy to find and predictable
Never get scared
Too linear

Oblivion:
Too repetitive and lacked visual flare
Needed a torch sometimes which was nice for mood and spooky factor
Had places that required thought to reach sometimes
Required exploration to find everything
Once in a while at least Oblivion kind of scared me with a dread zombie kind of sneaking up behind me
Loot was a little too similar (locked chests everywhere & worthless junk)