When I heard dark and gritty, I think harsh, realistic, unsentimental, bleak and quite probably depressing. In the context of fantasy, the closest fit seem to be Thieves World, the Black Company, Game of Thrones, Malazan, most of Robin Hobb's work and the Locke Lamora series. Characters tend to be morally conflicted and flawed. No good deed goes unpunished. Seemingly well-intentioned actions lead to domino effects and ultimately tragic repercussions.
While the art style in DA:O was slightly generic, I think it still largely helped contribute to a dark tone. Characters lacked comic-book proportions. Features were relatively normalized; Morrigan and Leliana were pretty, but not flawless supermodels, and the villain, Loghain, looked hard and haggard, not like some bishojo ubermensch. Ghouls and the darkspawn were frightening looking. The broodmother and the children, well... Nightmare fodder, to borrow from TVtropes, is pretty apt, I think. The cities and hamlets could have been grunged up a bit... More stained thatch and crumbling wattle, more dilapidated fences and broken stonework, more grunge and miasma, But it worked. It didn't actively work against a dark tone. And in the narrative, those aspects of darkness were present. Making the 'right' choice with the dwarven succession resulted in unforeseen negative consequences. The dark ritual, as mentioned earlier, was a means of killing your child's soul and perpetually unleashing evil strictly to slightly prolong your own life (as the Calling would soon enough take hold). Branka's Forge. Connor's fate. Dealing with Loghain. I think DA:O largely succeeded at their intent in creating a dark fantasy story and world.
DA2.... looks like it will be more of an uphill battle. The art style and animation actively work against it. The Rule of Cool has obviously been invoked and it uneasily coexists with gritty and dark. The movie adaptation of Watchmen was an excellent example of this conflict; Snyder stuck pretty closely to the story (obviously adapting the ending), but the fight scenes were re-envisioned in his 300-style hyper-dramatized form. Costumes, instead of obviously being cloth, were rubberized. Ozymandius... Ugh. Don't even get me started on Ozymandius. In making these stylistic changes, he heavily undermined a great deal of what the story set out to create in terms of its gritty portrayal of superheroes. It still kinda worked, overall, but I feel a good portion of the impact was lessened.
I hope that DA2 will continue to offer complex morality in the storyline itself. I just happen to feel that the art style and animation really don't do the author's any favors in helping them to fulfill that goal.