For me, it's not the dragons, nope, it's the Radiant Story feature! I think that's very original and unique and sound really deep, seems like quests won't be 'static' anymore and some objectives will be random/preferred to your playing style. That's awesome.
That, or the new levelling up mechanics. Where the more you use a type of weapon, you gain more skills towards that area; rather than having to begin a new game and make a new character to get it right.
How about you?