1) Castlevania SotN
2) Metal Gear Solid
3) Legacy of Kain: Blood Omen
4) Legend of Mana
5) Bushido Blade (1 & 2 together deserve one spot.)
6) Tecmo's Deception
7) Resident Evil (The first one the first time it came out)
8) Discworld
9) Twisted Metal (Mostly 2 but the others were good too)
10) Bloody Roar (Again mostly 2 but the first was good too)
Honorable mentions...
Loaded
D&D: Iron and Blood (So bad it was good)
Wild Arms
Lunar games (Mostly excluded from the actual list because PS1 was not their original platform)
Im sure there are more that Im not thinking about.