Symphony of the Night is awesome and is essential for any gamer. Along with Super Metroid, it is the pinnacle of the Adventure genre IMO.

if you don't already have, and like rpg, i recommend;

FF7
crono cross (currently playing)
crono trigger

I would say Xenogears, but that's not on the EU PSN. Get Final Fantasy IX. In my opinion, it's the only great Final Fantasy game since FF6. No emo protagonist, memorable characters, great soundtrack, great sense of adventure, and airships. You're welcome.

Wait a minute these games are on PSN ? 

Goddamn widely underrated gems.

It's been mentioned 200 times already but Castlevania: Symphony of the Night is the answer here.

I'd recommend Grandia, one of the greatest jrpgs ever made, fantastic lovable characters, great plot, and tight gameplay.

I've decided to make a poll of the games mentioned in this thread to give me definitive answer on what PS1 game to download.

Play Chrono Trigger!