I only recently completed the main story; the side quests have done a great job of keeping me occupied.
Story-wise, the ending is great, but action-wise, it's not as climactic as the end of the civil war quests.
The quests themselves in the civil war chain, other than the ending, annoyed me. The Battle for Whiterun was fun from the Stormcloak perspective, but the Imperial version was dull - all you do is fight Stormcloaks at the gate. And throughout the entire quest chain - on both sides - I killed just as many allies as enemies because they wouldn't get out of my fucking way. The forts were tedious. It would've been a lot faster and a lot more fun if I could run through the forts alone, especially with my stealthy characters, i.e., most of them.
I don't know what it is, but whether I'm rocking daggers, a bow, or my bare hands, I love sneaking around and taking people out, one by one.
Edit: That's the first tl;dr post I've made in a long time.