The first Darkness was one of the best games. It had the greatest voice acting that has ever been seen in a game, the graphics were amazing, and the story was, while lackluster of more original Darkness elements still managed to be great.
2 is…well, it's too different. The first was partially open world, and had much more of an adventure sense to it, while still keeping a dark and grim feel to it. There were entire sections where you wouldn't need to kill or shoot at anything for a fair amount of time. The second one on the other hand, is entirely linear. There are a couple of times where you are at Jackie's penthouse, but there is bugger all to do there, and character interaction is severly limited to a couple of lines per character.
The graphics is the one thing I was not looking forward to. Cell shading in video games is a severe graphical limitation. Sure, it makes a game look more like a comic, but unless the game goes as far as XIII did (I.E. With the sound effects coming up as words, etc), it does nothing but make the game look ugly in many parts. 2 however managed to pull it off rather well. If you stand still looking at a scene with no movement, it easily looks like it has been hand drawn. The problem with this, is that it makes the game look much less serious, and more quirky, similar to what Borderlands did.
The voice acting was still good, although no where near as emotionally involving as the first was. Don't get me wrong, the game definitly tried. And unlike most games that try, this one looks like they put real effort in, and it worked in a couple of scenes. Mike Patton, who voiced the Darkness, is the only voice actor to return, and Jackie now sounds less like an actual italian mobster raised in NY and more like some pissed off man in his forties (When he's supposed to be twenty three).
In the end, I can't say whether it's a good game or not. Some people will enjoy it thoroughly, and some will hate it with a passion. It gave me some entertainment, but not as much as the first, and like all FPSs these days, the single player campaign is pitifully short. I will say this though. Remember the ending of the first game where Jackie was consumed entirely by the Darkness- It does that again, only slightly different. And if a third game were to be made, there would need to be some actual answers.