I own all three (Steam gave them to me for free), but only played Two Worlds II and Risen.
I enjoyed Two Worlds II much more than Risen since I thought it was more RPG-ish (more loot, skill points, leveling up) where as everything in Risen was more much gold-oriented. In order to raise skills, you'd need to pay to train them. Combat was easier in Two Worlds II, resulting in a lot less death.
Both games are absolutely huge and look amazing. You'll easily put in 60+ hours just to play through once and the games are open enough to warrant several playthroughs if you like trying different builds.
Divinity II looked like a FF game to me (somewhat open, but more directed than the others), but since I haven't played it, I can't comment.
Oh, and Risen II is apparently awful according to reviews, so that may or may not affect your decision (I buy games all the time because of newly released sequels).
I don't really care for the flash deals and voting portion this year, but I guess after all the problems with using achievements last sale, Steam couldn't repeat that again. Most of these deals are ones that either come up a lot and/or are already being offered as the daily deal. Since it's not uncommon for someone to miss a single day of the daily deals, I almost fail to see the point of the flash deals. Maybe we could vote for one game for a 24 hour sale that wasn't going to be a daily deal...
Edited, Jul 20th 2012 12:20pm by xypin