Survival Horror via Wiki said:Survival horror is a subgenre of action-adventure video games inspired by horror fiction. These games mostly involve making the player vulnerable by providing them with less ammunition and fewer heavy weapons than other action games. Although combat can be a part of the gameplay, the player is in various ways made to feel less powerful than in typical action games, because of limited ammunition, health, speed, or other limitations.The player is also challenged to find items that unlock the path to new areas, and solve puzzles at certain locations. Games make use of strong horror themes, and the player is often challenged to navigate dark maze-like environments, and react to unexpected attacks from enemies.
I suppose that's what I think of most when I think of the genre. Just that feeling of hopelessness and the fear of the unknown. That certainly wasn't present in RE5 or Dead Space imo.