Dead Space 2 is the best game in the "Survival Horror" genre and the greatest video game sequel ever made.
Storyline:
Dead Space 2 takes place in 2511, 3 years after the original game. Isaac awakens in an Insane Asylum on "Titan Station" (or The Sprawl) to another Necromorph outbreak. He wonders why another Necromorph outbreak started, but his memories of what happened between Dead Space and Dead Space 2 are all gone. He is also still haunted by the death of Nicole and makes it his mission to save to stop the infestation on The Sprawl. I don't wanna give away any spoilers, but it has a terrific story.
Gameplay:
Now gameplay isn't too different from the original at first glance, but you quickly notice several improvements. First off Isaac's control is MUCH smoother and the controls are MUCH more responsive. Stasis is also much better now, do to there being an auto refill for it. Kinesis has also shown a big improvement. It's much faster this time around and can rip the blades off of dead necro limbs. Melee combat is much improved here, being more useful now and actually somewhat of a requirement. The biggest change here is of course the Zero-Gravity. It's MUCH better here than it ever has been before, as you now have complete control in Zero-Gravity. All of these were among my favorite sections in Dead Space 2. The "Strategic Dismemberment" combat is still the best way to kill necromorphs, but there are several other ways to defeat them this time around, such as impaling them to walls or shooting them into the vacuum of space.
Multiplayer:
You think I'd include this in the "Gameplay" section, but I feel it deserves it's own spotlight here. Here 2 teams of 4, humans and necromorphs, compete. The humans have a certain objective based on the map, while the necromorphs have to kill them before they can complete these objectives. The humans are all pretty much Isaac so obviously their gameplay is fantastic, though it's quite a bit of fun to use the Necromorphs. The 4 different types offer a nice variety. While this mode isn't as good as the single player, it's actually quite fun.
Graphics:
The first one looked amazing, the sequel looks even better. The lighting here is excellent, just like the original. The art style however is MUCH better here as this is a giant city compared to a space ship. The character models are much nicer here, Isaac being the obvious stand out. This is among the best looking games of this generation, and is another example of a game without a graphical flaw.
Sound:
The sound design is utterly fantastic. The games soundtrack is excellent, the sound effects are lovely, and the voice acting is just brilliant, Isaac's voice again being the stand out.
Bonus Content:
This version of Dead Space 2 comes with a move support version of Dead Space: Extraction. I did a review of the original Wii game, so I'm not gonna talk much about this here, but this version is the superior version with better visuals and better controls.
Overall:
Dead Space 2 is the best survival horror game ever made. It's well paced, it's scary, and it lets you connect to the main character better than pretty much any other game. Dead Space 2 is the best video game sequel ever made so what are you waiting for? Go out and get this game.