I'm going to make a solid case for Fatal Frame 2 since it's losing by a lot, and I kinda' suspect far, far more people on Era have played Resident Evil 2 and Silent Hill 2 and not Fatal Frame 2 (not everyone obviously, just none of the FF games have sold over 1 million copies, so one can deduct that probably most people have not played Fatal Frame).
Fatal Frame 2 does a few things better than SH2 & RE2 outside of just scariness I guess is the popular opinion (to be frank, I don't really think RE2, SH2 or FF2 are all that scary, but I guess if I had to pick which of them I thought was scariest I would give it to FF2. One of these aspects is I actually think Fatal Frame 2 has the best setting and art direction of these games:
I'll post more actual pictures through this post, but Fatal Frame 2 uses several interesting motifs in the game, which range from audio to visual to story. I would actually go as far to say that Fatal Frame 2 has more attention to detail in its environments than RE2 and SH2 as well, and does more interesting things with its level design. The other games do interesting things too, but the layouts between locations in FF2 are consistently well designed and more varied than the other 2. RE2 suffers from keeping you in the RPD for too long in essentially an 8 circuit, and Silent Hill 2 has some brilliant level design like the Historical Society, but also a lot of things I don't think are as well designed as they could be, like the hallways crammed with nurses and rooms full of them in the hospital or weird obtuse puzzles like the orange can drinking sequence. FF2 has this level of care and meticulousness to it that the other two games don't have in terms of its game design.
I also think Fatal Frame 2 is the most creative with its scenarios. It does this sorta' design where nearly every room in the game is designed with something in mind that's unique and interesting, so every individual room of the game can stand-out in the mind and has something about it that makes it interesting, and often one or two things to do in every room which are sometimes very varied from each other, and a number of rooms provide unique moments exclusive to that room. Silent Hill 2 has some variety in bits, but you really are doing a lot of the same things thought the game (more focus on narrative and atmosphere than gameplay by far, but what you mostly do in the rooms in SH2 is about the same), while Resident Evil 2 is more mechanically robust but the actual variety of the game is only a bit better than SH2 with mostly the same thing to go on, limited enemy types, and only the occasional boss or puzzle to shake things up, some distinctly designed rooms, but it's mostly got a groove it relies on. Fatal Frame 2 meanwhile is comfortable and confident in switching itself up, experimenting and exploring interesting situations and possibilities.
Again, I'm not voting and I'm not really sure what I'd vote for even if I tried, but I think Fatal Frame 2 one of its big failings here outside of people taste is going to be in how many fewer people have actually played it.