You make a great point about the cleanliness of the environments in Shattered Memories, and how that and the lack telegraphed fear moments pretty much undermined the horror of the game. It ended up feeling like an episode of Twin Peaks as a result, which is fine, but just not Silent Hill.
Also, the monsters were fairly generic: even if their appearances changed, their behavior didn't, so it didn't really matter. Maybe if in the next one, Climax codes four or five different types of beasts, with specific personalities, that alter based on the whole psychoanalysis thing, that would help. That, and add a lot more uncertainty (open a door on "normal" Silent Hill, and going into another room, without warning, and finding the Otherworld), grit, and grime.