Speaking of Skyrim, now that I've done all the questlines, here is my ranking of them.
1. Thieves Guild - deep, surprising, fun
2. Dark Brotherhood - still pretty dark. the Keeper is probably the best part of the whole game
3. Main - deep, but not terribly interesting
4. College of Winterhold - pretty deep, solid story
5. Imperial Legion/Stormcloaks - a lot of "go clear out this place", but with a kickass final battle
6. Companions - other than [spoiler], not very much to it