I recently had a chance to look back at the first Resident Evil and Silent Hill. I have to say that while I enjoyed them both considerably, neither of them is what I would call frightening. I have since played Silent Hill, Silent Hill Origins, Silent Hill: Homecoming, and Silent Hill: Downpour, but I haven't played the most beloved of the franchise yet, which is why I wouldn't consider what I say as conclusive. I have played Resident Evil, Resident Evil 0, Resident Evil 4, Resident Evil 5, Resident Evil 6, and Resident Evil: Revelations. While I think Resident Evil 4 is one of the best video-games that I have ever played, I am not convinced that it's actually frightening. I wasn't afraid or startled, and I often wonder exactly why that is. Maybe it's because I find it difficult to be afraid when I am also asked to think analytically and cognitively to solve a wide array of puzzles. I can't be afraid or shaky because the game-play demands something different entirely, and because of that, while it might technically be the best overall experience, I can't call it the most horrifying experience.
Titles such as Outlast, Saw: The Video-Game, and Dead Space all have elements of horror that are worth regarding. Outlast is a straight-up horror, and Saw: The Video-Game is actually a guilty-pleasure of mine for its terrific adaptation of the horror franchise inspiring it. As for Dead Space 2, while I wouldn't necessarily call it too frightening, I would say that it's an absolutely amazing game. Same for The Last of Us, which I often regard as my all-time favorite. The only title that ever really scared me on any level is BioShock and that was because of the certain novelty that I approached it with. There was something menacing about The Great Daddy, as well as the mysterious atmosphere I was forced into. Whether or not that feeling would be replicating for me in a second play-through is irrelevant, the fact is, I was actually a little shaken up with it initially and that's what matters. I would say that BioShock is the closest I could come to an actual answer.
Another title that I think is worth the mention is The Evil Within, which, while isn't exactly to the same standard as BioShock, Resident Evil 4, or Dead Space 2 in-terms of overall experience, actually offers up a commendable amount of horror-elements. I would go as far as saying that from a certain standpoint, it is the best horror video-game that I have ever played. Still, I don't have the credentials to make that comment. I recently bought Alone in the Dark: New Nightmares,Fatal Frame, Resident Evil 2, Slender: The Arrival, Manhunt, Amy, and am eyeballing the release of Dying Light, but after that, I'll be more equipped to make my decision.