As a Silent Hill fan, I'm tempted to say "Resident Evil" for its horrid plot, clichéd premise, voice acting and lacking-in-fear gameplay, until I remembered that's what made it good.
So I'm going with Dead Space, because
A) It's probably going to surprise someone, who may in turn flame me
B) Because that same person probably found the plot intriguing, when in fact it felt campier than Resident Evil, albeit without the hilariously awful quality that pervades the former
C) Because it's still touted by many as scary, when it relies solely on violent visuals, jump moments and a complete disregard of subtlety
D) Because many compare it to Alien (including the developers, who cited it as prime inspiration material) despite a jump in quality.
E) As Yahtzee said, it's repetitive. Really, really, really repetitive.
By no means is this a flame post, maybe a general argument against the modern direction of Survival horror, but by no means designed to bait trolls. Perhaps I've played worse, but Dead Space seems to stick in my mind whenever this question is asked solely because I resent the turn one of my favourite genres of the 90's has taken.