Dead Space is a pretty good IP, but my opinion differs. For me, Demon's/Dark Souls is the best IP of this generation. The funny thing is, is that both franchises are steeped in mystery, tension and thrills, with Demon's/Dark leaning more towards dark fantasy lore and Dead Space horror.
The thing is, with Dead Space after a while you can predict where the necromorphs are going to jump you, which areas are "dangerous" and which you can let your guard down. There is that suspense, but it's suspense tempered with the knowledge that something is going to scare you soon.
Souls, on the other hand, is fabulous at implementing a Hitchcockian sense of suspense, where we are given some information but sometimes nothing actually happens. Or, at least, not right away. It can be maddeningly tense in the Souls game when you are carefully treading through a winding maze of dark corridors, your only light a glowing crystal at your waist, not knowing where the next enemy will be. Is it around the corner? Or is there a fall ahead of you? A trap? Nothing at all? I found that Dead Space takes it's cues a bit more from modern Hollywood shock films, while Souls employs a bit more of a slow burn.
Both have great payoffs, but I find Souls to be more engaging. However, these two franchises strike me as cousins, in a way. Souls has mastered the fantasy niche of survival thriller/horror and Dead Space has cornered sci-fi terror. Both great franchises in my opinion, but I have to give the edge to Souls.