So, after playing Skyrim for a while now, I have to say I am really disappointed by how most of the guilds and plotlines have gone really dark.
Some points:
1) I loved playing thief characters in both Morrowind and Oblivion -- but now the guild is really low-life, and you have to sell your soul to a daedra in order to complete the questline. I really don't want to be a Nightshade wraith in the afterlife! Sovenguard looks a heck of a lot better. It has nothing of the delightful flare or the Grey Fox ("Capital!") of Oblivion days. It is just dull repetitive quests filching for low-life crooks in a sewer, Just so you can give your soul over to guard a daedra princess who really does not even care about you much.
2) The Dark brotherhood is even more dark than before. I honestly liked it in Morrowind when we could be Morag Tong -- they at least had some code of honor to them. The switch to Dark Brotherhood in Oblivion was a downgrade, in my opinion, and it went down from there in Skyrim. You could have at least made the option to destroy the Dark Brotherhood be as interesting a quest and have as much content as the option to join them!
3) All of the Daedra princes have gotten darker. I HATED being trapped in the house by Molag Bal -- not even the option to reject the quest! That really, really stinks. I had to go back to a prior save just to avoid the quest. Hermaeus Mora -- again, not really much choice in the matter. Namira, the same -- except in this one we now have to be cannibals! Yuck. It was much better in Oblivion when you had to activate the statues to make the quests start. Just give us a choice, for crying out loud!
4) You have all of this great overland scenery, but most of the plotlines involve going into crypts and fighting draugr over and over again. A little variety, a little more daylight, would be really welcome in the next game (which I hope comes out).
5) Both factions, Empire and Stormcloak, are pretty pathetic. The Empire is corrupt and a Thalmor toady; the Stormcloaks are racist, narrow-minded, and bloodthirsty. And the Thalmor are nasty too. What a disappointment, to make elves be such nasty characters, for someone who grew up on Tolkein and loving things elven. But in this game, you really feel like killing every Thalmor you run into.
6) The Fighter's guild was replaced by the Companions, so now if I want to be a Fighter-build I have to be a werewolf. Yuck. No interest in feeding on corpses, or becomming a monster, just so I can be a fighter. It is great to be a noble knight-type character, but not at the price of becoming a werewolf.
7) I know it has been treated a lot in the forums, but the racism got a bit out of hand in this game. To many overtones of Aryan supremacy and Xenophobia. It is not necessary, and does not help the game.
8) I like RPG's where a player really has an option of what direction to go, and the options are all equally interesting. In this game, however, once you finish the main quest, and perhaps the mage quests, a good-leaning character is really out of much interesting stuff to do. Even Shivering Isles gave us a choice between mania and dementia, and that is Sheo's realm! There should be at least as much choice in the noble realm of the Nords!