10/10 Seriously awesome. Buy it.
Basically what EA Redwood Shores have done is recreate Bioshock and set it in space. But the overall effect is much better than Bioshock.
It's a shooter/horror, starring you as Isaac, an engineer sent along with a rescue team to find out what happened to the USG Ushimura, a deep-space 'Planet Cracker' class mining vessel.
Things go wrong roughly 20 seconds into the first cut-scene, and from there on you're following the orders of what's left of your team as you attempt to get the Ishimura's systems back online, fighting off the hordes of beasties (Necromorphs) infesting the ship and trying to find out what happened to your girlfriend who was working there as part of the 1000-strong crew.
What makes Dead Space better than Bioshock is Isaac, he's an engineer, and all the weapons you get are things an engineer would be handy with so it's slightly more believable. You get stasis modules to slow down fast-moving machinery, you get Plasma Cutters for slicing legs off at the hips and arms off at the shoulders and heads off at the neck, flamethrowers for lighting enemies up en masse, Rippers - remote controlled saw blades for, that's right, you guessed it! And many more.
The fun comes when you combine different abilities, like when you've only got 4 plasma cutters left you can hit a Necro with stasis and take your time shooting off its limbs one by one then finishing it off with a nice and gory curb stomp.
You can keep your eyes open and deviate from the 'engineer roleplaying' because scattered around the Ishimura you'll find some neat military hardware to put to good use should you wish to, like the rapid-fire and extremely deadly pulse rifle.
Navigation throughout the mammoth spaceship is aided by a neat menu system, press Back on the control pad to bring up an instant 3D holographic projection of your location and objectives, zoom in and out and rotate it around to your heart's content, it's impossible to get lost especially as you can bring up a 'breadcrumb' trail at any time to show you where to go next.
Exploration off the beaten track is rewarded with special units that you can use to upgrade your environmental suit with more air and HP, or your weapons with more damage and other neat features. You can also find credits lying around which you can spend in the Ishimura's Store, outlets of which are scattered around each level. The store stocks new weapons, allows you to convert any schematics found into buyable hardware, store extra ammo/items you've picked up and sell any goodies that you've found for extra credits. Your suits have limited inventory so you've got to think carefully about what to carry around so you can pick up more stuff, and there's no unlimited ammo so aim carefully.
There are a host of neat ideas in Dead Space to liven up the gameplay. You've got zero-G environments where you can kick off one wall and land on another and watch as the whole room spins to your new perspective, ceilings become floors, walls become ceilings, doors you didn't see before can now be reached. Later on it gets trickier, Necromorphs can also jump from walls to ceilings and you can have great fun blasting them out of weightless vacuum mid-flight. Later on again you get the same thing, with the addition of zero-air which makes you watch your air meter on the back of your suit (next to your health bars also on the back of your suit) and adds a whole new dynamic to these areas.
Probably the neatest idea of all is the complete lack of HUD, all you've got onscreen is you, the environment, and your crosshairs which vary in type depending on your current weapon selection. This allows you to make much better use of your screen, you'll be able to easily see an explosive cannister next to that wave of little beasties heading for you, you'll be able to look all around you and notice those cabinets that you missed before, you'll be able to admire the full gory detail from third person perspective as something flies out of the wall towards you, grabs your leg and... don't worry, you'll find out.
In terms of immersion, think of the first time you played Resident Evil and the dobermans jumped through the window, or Bioshock the first time you opened a safe in an empty room then turned around to discover it wasn't as empty as you thought. Now multiply by 10 and add a constant stream of distant bumps in the night, nails scraping down a blackboard, a dash of violins constantly building up into a crescendo and play it crouched in a pitch black air duct whilst the hairs on the back of your neck stand up because you're pretty sure there's an Alien behind you. With sharp teeth. Breathing down your neck. That's pretty much Dead Space, scariest creepiest and most horrific game I've ever played. Oh, and blood, lots of it, everywhere.
Longevity is mainly in the achievements (get every weapon, upgrade everything, kill x enemies with y weapon, dismember 1000 limbs, beat the game with only the Plasma Cutter etc.,) and you can stray off the beaten path even more to get the more obscure achievements - zero-g basketball, anyone?
Basically it's the best new IP out this year by a few miles, considering it comes from the mighty Electronic 'milk those sequels' Arts is even more surprising, and considering I bought Fable II the same day as my most anticipated game this year and haven't really been playing it because of Dead Space it's all a bit overwhelming, really.
Single player all the way, no co-op or online here, but the beautiful thing here is you won't care, it doesn't need multiplayer, it's a game you're meant to play alone.
My only gripe would be that Isaac doesn't have a voice. Given that he's an engineer and constantly being sent to his certain death with every single objective you'd expect him to mutter about the Engineers' Union and hazard pay. Other than that it's the most perfect shooter I've played in a long, long time.