Third parties, CD format, third parties, third parties, and third parties. The PS1 was the console where third parties really cut loose. Sony provided Eidos, Capcom, Konami, Square, etc. a console that they could go crazy with. And go crazy, they did. Boundaries were pushed, new ideas were realized, and Sony (and gamers) reaped the benefits. Final Fantasy 7, Metal Gear Solid, Resident Evil, etc. these were games that Nintendo's 64 bit console was just incapable of producing without some serious technical limitations (I know about RE2 for the N64. Shut up.).
Sony didn't really do anything special. Nintendo cut their own balls off by sticking with the cartridge format and Sega screwed up by creating a console with the word "Sega" on it (gamers were pissed with Sega by the time the Saturn launched.). With no place else to turn, the fairly solid PS1 was the heir to the throne. If you were a gamer without a PS1 from 1996-2000, I really pitied you.
