I just played it for the first time ever a couple of weeks ago, after being a huge fan of the original. And it is by no means the worst game I've ever played, and so certainly not the worst game out there. It's not even a bad game, not exactly. But it certainly isn't anything more than mediocre.
The combat is okay, personally, I didn't see much difference between DA2 and DA: Origins in that regard. I may have paused and micromanaged a bit less in this one, but that's about it. The characters are also okay. I enjoyed Varric, Isabella, Aveline, and Fenris, although I found all character interactions and romances severely dumbed down compared to Origins. Halfway through the second Act I had maxed out friendships with all of my people and thereafter could simply ignore them. I also didn't mind the storyline. It wasn't epic or particularly interesting, but I liked building up Hawke from a nobody into a powerful individual. However, this is a very tenuous liking, because the story was undoubtedly disjointed and atrociously paced.
And those are the good things I have to say about the game. Beyond that there are the graphics to consider, which seem hardly improved from Origins, and if anything are possibly worse! Everything looks bland and unfocused, as if we really are listening to Varric's story and he just didn't feel like bothering with the descriptions. And speaking of the environments, they're all the same. Bioware seems to have an issue with this, as it is also found in Mass Effect and Mass Effect 2, but nowhere is it as terrible as in this game. 90% of the areas are recycled, and not just recycled but blatantly recycled. There's simply no excuse for such behavior for a giant and famous company. If lone modders can create environments for Elder Scrolls games that are more interesting and diverse than something a leading company creates, then there is a serious issue.
So all in all, it's not that DA2 is the worst game ever... It's more like it's the worst use of resources ever. If some no name company operating out of a garage created it, it would be an achievement. But Bioware has experience, money, and talent, so for them to create something like this is just plain embarrassing. That's why people feel so vehemently about it, and rightly so.