Scary games? Well, in no particular order....
Friday the 13th (C64)-A classic, particularly when the bodies start to pile up & the fright-o-meter starts climbing. A rare game where the bugs (like losing your weapon if you change to another), enhanced things with random events! Why doesn't someone do a modern-day 3D version-I'm sure the concept would work well for that B-grade atmosphere.
Ghettoblaster (C64)-Although not exactly "frightening", towards the end of the game with numerous baddies running around, the flickscreen scrolling would lead to some interesting finishes!!
Resident Evil's 1-3(PSX)-Brilliant. In all three games I'm sure most people must've encountered portions of each game that you didn't expect to happen.
Final Fantasy VII(PSX)-Again, not something you might be scared at every second of gameplay, but for the major set-piece monster battles at major parts of the game I enjoyed (in hindsight!), having to take on the major boss fights & wonder how long it'd take to defeat some of those monsters. (eg:Ruby/Emerald weapons).
I only ever played a demo of Darkseed, but well recall the "headache interlace GFX syndrome". Was always curious about seeing more but that problem must've been a nightmare to try & play thru-maybe it was supposed to be an unadvertised "interactive" feature for the headache suffering in the game!!