Noo! you can't even draw a line between them.. this is totally different alot of cool new features (Side quests) that are more variety and more fun.. Instead of killing guards that harass people.. now you get assassins mission, run after pickpocketers, race missions, delivery missions and more! And you get to customize your charcter!!!!!!!1
And the main quests are ofc the same that you need to kill them (atleast as ffar as ive come) but the way you do it is more awesome:) (
Sorry for any bad engliesh here