What faciton, person, quest, etc... do you find to be simply fantastic? You can even dislike the content based on what it is, so long as you appreciate it based on how it was done. I know that sounds a bit silly but, my example may help:

I think the best, nearly perfect thing about the game is the Dark Brotherhood. You actually end up caring about these people, the plot progresses in a sane manner (well...as sane as anyone involving Cicero can ever be...) the characters are actually interesting, even in their mundane areas. ("Heres your payment. I could do this all day.")

there was no Super-Power magic item vanishing or the quests ultimately resulting in little change like some of the other factions. You honestly ended up caring about these people.

But it became perfect for me when I realized: Astrid broke each and every Tenant. To do so is to invoke the wrath of sithis, as a well known character said. It got even better when I realized that,yes, I had to kill one person to get out of the shack. And there were four NPCs.

Flawless Victory on that one, Bethesda.

So how about the rest of you? remember this isnt about something that's good, or fun. Its about something that works perfectly for what it was aiming for, even if you didnt like it (I don't care for assassinating NPCs personally.)