If they do make a 3rd game I would prefer it to be more like the original. I missed the free roaming elements of the original, the use of stealth with the creeping dark tendril attack and the realistic graphics. Yeah! I get the fact that the game is based on a comic so the cell shaded effect seemed the natural choice. My problem was that this was not used in the original so it didn't seem like a sequel but rather a different game based on the darkness, which is like the difference between the new batman game based on the movie compared with "Batman Arkham City". Continuity goes along way in game and movie franchises.
The darkness 2 was too arcade like for my taste. Good story lines make epic games. If the story line in a sequel is not as good as the on in the first game there is a problem. If a developer doesn't know where next to take a character's story they should probably leave it alone. A good example of quitting when ones ahead would be the "Uncharted" series. Drake's story was told, Naughty Dog move to next project, "The last of us", Cole's story was told in "Infamous 2", they finish the franchise. Sometimes developers just make game follow ups to make money of the success of the originals. I didn't think Max Payne 2 had as good a story as Max Payne 1. I lost interest in the Max Payne sequel's story in the same way I lost interest in the darkness 2's story.