This is tough. I'm pretty much a Nintendo fanboy, but Sony has always been my #2.

I originally had a N64, then later got the PSX. Each system had many great games. In particular, the PSX had the Final Fantasy series, Street Fighter Alpha III. The N64 had a ton of great games, as well, Super Mario 64, Mario Kart 64, Doom 64, StarFox 64, the LoZ games.