Without doubt, PS1, By a country mile:
Final Fantasy Tactics/Origins/Anthology/7/8/9
Saga Frontier
Legend of Mana
Front Mission 3
Breath of Fire 3/4
Spyro 1/2/3
Mega Man Legends 1/2
Alundra
Castlevania: Symphony of the Night
Vagrant Story
Tekken 1/2/3
Tony Hawk's Pro Skater 1/2/3
Brave Fencer Musashi
Suikoden 1/2
Tomba 1/2
Metal Gear Solid
Twisted Metal 1/2/3/4
Legacy of Kain: Soul Reaver
Medievil 1/2
Techmo's Deception 1/2/3
Crash Bandicoot 1/2/3
Ape Escape
Monster Rancher 1/2
Ridge Racer
Wild Arms 1/2
Gran Turismo 1/2
Wipeout 1/2/3
PaRapper the Rapper
Valkyrie Profile
Star Ocean 2
Dance Dance Revolution
Armored Core
Mech Warrior 2
Diablo
Metal Slug/X
Battle Arena Toshinden
G. Darius
Rayman
Grand Theft Auto 1/2
Threads of Fate
Street Fighter Alpha 1/2/3
Worms
Jade Cacoon
Dark Stalkers 3
Guilty Gear
Tactics Ogre
Jumping Flash 1/2
3D Lemmings
The Misadventures of Tron Bonne
Lunar: Silver Star Story Complete
1/2/3 Xtreme
Tomb Raider 1/2/3/4
Parasite Eve 1/2
Azure Dreams
Megaman X 3/4/5/6
Guardian's Crusade
Nuclear Strike
Vandal Hearts
Tales of Destiny 1/2
Future Cop: L.A.P.D.
Gex 1/2/3
The Legend of Dragoon
RPG Maker
Chocobo's Dungeon 1/2
Nightmare Creatures 1/2
Rampage World Tour
Grandia
Primal Rage
I know there are like 2500+ other PS1 games, but those are just some fun ones off the top of my head. :P
