Now see, Im torn here. Horror is my favorite gaming genre & I've played at least one game in each series listed in the poll above.
Silent Hill was a fantastic experience- I rented it first, played through it by candlelight using a guide, but that didnt ruin anything for me- I bought it as soon as I found it used. Since then I got SH2 the day it came out or soon after, & right now Im working on the secret "UFO" ending in SH3. It's gonna be a b*tch getting through the subway & home using only the Sexy Beam! Havent played SH4 yet.
My first experience w/ Resident Evil was w/ the Directors Cut DualShock version, I'd bought it (w/ Diablo) as my first PS1 games (I got on the bandwagon late.) I was walking along, wondering what all the fuss over this game (& how scary could it be?) was about, when the f'ing dog smashed through the window. I guess that did it for me. I was hooked on survival horror from then on. DIdnt care for RE2 or Code: Veronica X but RE3 was OK. Working on RE: Dead Aim w/ a Guncon2 right now.
Fatal Frame & Clock Tower are close runners up- Ive only played the 1st FF & I'll say it's best done using a surround sound system & leave it at that! The first Clock Tower is obviously dated but still a good game. IMO they did a good thing w/ CT3, though gameplay is a bit repetitive & simplistic. The cinema of the little girl being bashed w/ a sledgehammer still shocks me.
I enjoyed the first "D", but once I figured out what to do I got playtime down to less than 2 hrs- ZERO replay value. I sold it for 5x what I paid. I started D2 on Dreamcast but, as so many of my other games, cant find time to get back into it- & from recent posts here, I know I have to!
I rented Alone in the Dark for PS & got to the 2nd disc, but IIRC a glitch prevented me from progressing farther, at he circle of stones/steles. I got it used last year, & have since finished the Carnby storyline & began Aline's, but again- it's something I'll have to find time to get back into.
I started Siren awhile back, but got tired having to do the little vignettes repeatedly. Trial-&-error gameplay kinda bugs me. Maybe I'll get back into it someday.
Some others not mentioned that fit the genre & I highly recommend: Echo Night & Juggernaut (PS), Neither are really jump-out-at-you scary, but just give you that kinda creepy feeling. Juggernaut is a 3-disc game & has more of that "D"/Myst feel to it. EN's graphics are kinda weak & old-timey, but that fits the game's storyline. I picked up EN: Beyond for PS2 but again...havent had time to play!
Ooh, looking back on this, sorry for the length- I got kinda carried away.