Dead Space, to me, is an almost brilliant series, and one where the developers don't quite ever manage to focus on the best elements.
The first game is clearly a giant sloppy drooling fan remake of System Shock 2, and that's no bad thing. However, there are a number of design decision problems that stop it from being quite there. First off, the weapons. Sure, there's a wide variety of them and they're reasonably meaty and satisfying to use, and the fact that Isaac is slow and severing limbs is the new headshot makes the game tense and shapes the combat and makes it about managing threat, chopping legs to slow down horrible space wotsits and running around to avoid being hurt. But not only do you not need the weapons ever because the Plasma Cutter does everything, it's actually bad to carry more than the Plasma Cutter, because the game (almost) only gives you ammo for weapons you're actually carrying. Only carry the Plasma Cutter, only get plasma ammo, oh wait the resource management element of survival horror has just disappeared out the window. Also you can focus your power nodes on only upgrading the Plasma Cutter, so it's more useful, versatile, and efficient.
Likewise, the story, there's very little focus on Isaac's story throughout the game, even though the basis of it (he knows from the start that something bad is happening on the Ishimura, and he knows Nicole is dead but is in denial (yeah, spoilers, the game's a million years old get with the times). There's a fair bit of story potential in there, but it's not strongly realised and the game is mostly too busy with space scientologists to exploit the part that could have been good.
Dead Space could have been the new Silent Hill 2, but it wasn't.
Dead Space 2 upped the combat ante a little with some fun new enemies (though twitchers are gone and only in the DLC), but since Isaac is sprightlier now it feels mostly a little easier (and now you can justify two weapons, the Plasma Cutter and the Patrol Rifle, but you don't need any others... Also, the game became a corridor, to the great detriment of the suspense, DS1 had the old System Shock structure where you were relatively free to wander the current level and there were two or three things you could approach in any order. That's good for a survival game, it means that the player feels like they are choosing the risks to take themselves, even if they actually have to go everywhere anyway, if you go to objective A and something horrible is there, it feels like it was your fault for going there. It also makes the setting feel more like an actual place which you become gradually familiar with.
So, yeah, the first one had a lot more promise than the second delivered on, even though the second is still a good game, and it's not the best new IP of this generation because it's not called Bayonetta.
