Can you give a list of some good RPG games for the PlayStation?

I’ve played so many at this point I’ll divide them into tiers (I’m assuming you mean PS1).

S Tier (All time great)

Suikoden II (1999)
Xenogears (1998)
Chrono Cross (1999)
Final Fantasy Tactics (1998)
Final Fantasy IX (2000)

A Tier (very good / excellent)

Star Ocean 2 (1999)
Saiyuki: Journey West (2001)
Ogre Battle: Limited Edition (1997)
Breath of Fire III (1998)
Breath of Fire IV (2000)
Brigandine: The Legend of Forsena (1998)
Thousand Arms (1999)
Tactics Ogre: Let Us Cling Together (1998)
Tales of Eternia (2001)
Final Fantasy VII (1997)
Diablo (1998)
Legend of Legaia (1999)
Valkyrie Profile (2000)
Azure Dreams (1998)
Vagrant Story (2000)
Lunar Silver Story (1999)
Lunar 2 (2000)
Grandia (1999)
PoPoLoCrois Story II (2000)
Tales of Phantasia (1998)

B Tier (solid / decent)

Super Robot Wars Alpha Gaiden (2002)
Master of Monsters: Disciples of Gaia (1998)
Tear Ring Saga (2001)
King’s Field III (1996)
Kartia: World of Fate (1998)
Front Mission 3 (2000)
Dragon Valor (2000)
Arc the Lad II (1996)
Arc the Lad III (1999)
Threads of Fate (2000)
Tales of Destiny (1998)
Brave Fencer Musashi (1998)
Persona 2: Eternal Punishment (2000)
Langrisser IV (1999)
Wild Arms (1997)
Vanguard Bandits (2000)
Vandal Hearts II (1999)
Parasite Eve (1998)
Parasite Eve II (2000)
Legend of Dragoon (2000)
SaGa Frontier 2 (2000)
Shadow Tower (1999)
Brave Prove (1998)

C Tier (average)

Hoshigami: Ruining Blue Earth (2001)
Guardian Crusade (1999)
Goemon: Space Pirate Akogingu (1996)
Beyond the Beyond (1996)
Alundra 2 (2000)
Baroque (1998)
Koudelka (2000)
Wild Arms 2 (2000)
Digimon World 3 (2002)
Jade Cocoon (1999)
Dragon Quest VII (2001)
Shadow Madness (1999)

My top 25 would be..

1. Suikoden II
2. Final Fantasy Tactics
3. Xenogears
4. Final Fantasy IX 
5. Chrono Cross
6. Star Ocean 2
7. Lunar 2
8. Breath of Fire III
9. Breath of Fire IV
10. Valkyrie Profile
11. Lunar Silver Story
12. Tales of Eternia
13. Brigandine: The Legend of Forsena
14. Final Fantasy VII
15. Legend of Legaia
16. Grandia
17. Tactics Ogre: Let Us Cling Together
18. Thousand Arms
19. Azure Dreams
20. Saiyuki: Journey West
21. SaGa Frontier 2
22. PoPoLoCrois Story II
23. Persona 2: Eternal Punishment
24. Vandal Hearts II
25. Vanguard Bandits
26. Kartia: World of Fate