Best game on PSN is Syndicate Wars! well providing you can get 3 other humans to join you.
On the whole I think the list of PS1 games available is tragic (UK store at least) most of them are garbage and some classics just aren't there.
Why is Tekken 2 there when 3 was king? where's Ridge Racer, Gran Turismo, Parasite Eve, Crash Bandicoot 3, any Resident Evil, Die Hard Trilogy, Wipeout 2097 (we only have the poorer 1st one) etc..
It's been out for years and the choice of "Classics" is a shambles and half of them aren't even good (back then or now).