Thieves, Companions, Mages, or Assassin's? Which did you enjoy most?
If I have to pick one, probably Thieve's Guild.
But with that said, it was nowhere as good as Oblivion's Thieve's Guild.
Besides the initiation quest, the whole thing felt like a confused chunk of the mainquest.
Far too much combat, and not enough stealth or.. well
thieving.
And all that business with Karliah and Nocturnal felt silly and forced.
The guild is supposed to be a group of thieves indirectly fighting the law and making a fortune, not magical servants of some crazy [censored] who wants you to kill a bunch of robots and steal one of Buddha's eyes.