Mystery is a great medium through which one can create an interesting videogame. A sense of mystery, which stems from the fear of "The Unknown", is oftentimes a driving factor of the game's immersive dimensions such as horror and suspense. When something is unknown, it is a natural tendency of the player to seek to identify it as much as possible (which is part of mankind's evolutionary psychology. One must always be quick to figure out where exactly are potential predators that are capable of threatening one's own survival, right?). And in the process of doing so, the player inevitably gets engaged and becomes part of the game.
A typical horror game would give the player a bunch of jump-scares, random indecipherable hints scattered all across the place (without any congruent structure of meaning), and other unexpected events for the purpose of constantly providing the player's primeval survivor brain with impulsive doses of Adrenaline. This strategy of keeping the player's tension, however, eventually becomes a series of lame gambling sessions as the player figures out that such jump-scares are just chance-based losses in the main character's stats/inventory (not so distinguishable from buying/selling random stocks at random points in time).
A more replayable horror game would create a system which literally contains some solid predatory entities in it, instead of just throwing a bunch of random scary events at the player's face. Instead of just random ghosts popping out of nowhere and then disappearing like holographic images, it would have social lounges, hubs, restaurants, hotel rooms, and fitness centers designed for ghosts to hang out with one another while discussing their own plans to screw up the player. Now this will force the player to understand the "system" (i.e. social structure) of these scary ghosts instead of just fearing the mere dice-roll chance of their unprecedented attacks.