As a horror games fan i would recommend :

1- Fatal Frame Trilogy "people like the first more"

2- The suffering 1 " a real gem , the second was about action more than horror"

3- Siren 1 " and maybe 2 , i did not buy it"

4- Clock Tower 3 " i played it once for half an hour , a japanese version so i did not know what to do"

other genres :
Suikoden 3 and 5 , SMT:nortune "playing it now" , Indigo Prophecy "really good did not finish it till now , get the pal version and you will see a sex and nudity scenes , not in US version "