I'd agree with you there....
...If not for the massive differences all round in the game, some of them good, some of them bad. Sequels are frequently massively different. For instance Star wars I through III were utter bollocks. I'd never review something as a great Star Wars movie, I would review it as a great MOVIE, even as a continuation of a series, a product should be judged and reviewed on it's own. There's nothing wrong with comparisons, I agree, the first game was better in comparison, but the game should not be reviewed in comparison.
I blame a numerical rating system for this as it forces people to assume that a title rated 8/10 is identically as good to another 8/10. A good example of this is that on Metacritic, the user rating for Halo 2 on PC is 5.2/10 Dragon age 2 is scored 4.1/10 purely because some people are rating it 0/10 Can you honestly tell me that a weak Xbox sequel ported to PC 3 years too late is better than this game?
The fact is, people have rated this game based on the amount they liked the first game, which many hardcore RPG players I know called "baby's first RPG" Origins wasn't some mystical godlike game it was just a very good game that was kind of dumb. I'm smart enough to not think I'm above playing games which are kinda dumb.
Additionally, and finally:
While you say it's a continuation of a series, again, I'd point out that that's not really a fair comparison, it's not "the continuing adventures of", it may as well not be a sequel to Dragon Age: Origins, it features very few of the same characters, it's almost entirely set elsewhere. Maybe it'd be better to think of it as a spinoff?
Good game, sadly flawed. Sequel to a great game, Sadly flawed.