IMO Divine Divinity is the best of the Divinity games so far. I don't think Original Sin will top it. The reasons? Turn-based combat and artstyle. So many top-down games recently have that artstyle as opposed to a more realistic one as found in Divine Divinity. Meanwhile, turn-based combat has never been a favorite of mine. This is all a matter of preference though. It's a given that Original Sin will have good writing, quests, atmosphere, story and characters but I'm unsure about the combat but who knows, I might come to enjoy it.
Either way, if Original Sin features the same exploration as Divine Divinity but in an even bigger world then there's going to be lots of fun to be had.
