Skyrim is big...big and empty with no real challenge, and is easily forgotten *since nothing really catches your eye except for good visuals* Same was with Oblivion and Morrowind, i don't remember anything that happened in those games since it seemed so unimportant.
Dark/Demon Souls on the other hand, always keeps you occupied be it challenges/puzzles or Grind/coop. I still remember when i first killed the first boss in DS like it was yesterday. I already played for about 400 hours in Dark Souls and i never got bored, not even once. There is always something to do, someone to kill, something to talk about on forums.