I have Dead Space, and I really quite like it so far. I'm ... 7? chapters in. I was skeptical at first; I thought initially that it would be too much like Doom 3, which I dislike rather strongly. But I was pleasantly surprised. I doesn't have me so scared so badly that I feel like quitting (Like S.T.A.L.K.E.R. did in those underground segments), but several times so far I yelped out loud, and I find myself acting very cautious. The weapons are unbalanced, yes. But, if you didn't know, you mostly receive ammo for the weapons you are carrying ... meaning, carry one or two, have tonnes of ammo but limited options for whatever threat you might face. Carry four, the max, be constantly scrounging. I carry four, and I'm constantly having to switch to my ripper, which uses ammo conservatively, but is a beast to control when fighting multiple critters.
As others have said, the game oozes atmosphere, sometimes in a System Shock 2-esque way. You find audio and video logs of long dead crew members, and sometimes you can hear disembodied voices. The scrawlings of madmen can be found on walls everywhere. (Incidentally, did anyone else see the alien alphabet translation? I saw it, but felt too tired and antsy to write it down.) You can hear your characters heart beat speed up and slow down after you fight and defeat an enemy. And I ADORE the lack of a HUD. It is very slick, and really helps you feel like Isaac in a derelict spaceship and not some chubby nerd in his comfy chair. I hope other developers try this sort of thing in the future.
And the music. FUCK the music. Glissandi harmonics in violins is not pretty.
There are flaws, but this game well makes up for them with polish and design. Well worth a purchase, and I plan on playing through at least twice.