…Oblivion: that it was too High Fantasy for my taste. Level scaling (though Tribunal had done this before). Psychic guards. And worst of all: no collectible light sources! Interior decoration was a real drag
Luckily, there's a debugging shortcut that cycles you through the important locations of a dungeon… that cheat is a necessity, because you WILL get stuck. If you don't fall through the floor first, of course.