For RPGs, PSN already has:
Xenogears (Japan only)
Lets say PSN has hypothetically lined up, for the next few months, available for both PSP and PS3 ($5.99 USD each):
Tales of Destiny
Tales of Eternia (out of print on UMD I think)
Valkyrie Profile (again, out of print on UMD I think)
Blood Omen: Legacy of Kain
Legacy of Legaia
Breath of Fire III (out of print on UMD)
Breath of Fire IV
Multi-disc games don't seem to show up on PSN for PS3/PSP, so I didn't include the obvious multi-disc RPGs everyone would want (Final Fantasy VII-IX, Thousand Arms, Lunar 1 & 2, Grandia, etc.)
Do you, on a scale from 1 to 10:
1: Don't care in the slightest -- old PS1 RPGs? Who cares? You haven't even heard of most of them, or you played them all, and now they are old news.
10: Run out and buy a PSP or PS3 right now, knowing your RPG addition will be covered in style for many months to come.
I'm curious, since this is actually the main reason I purchased a PSP (I missed out on a lot of PS1 RPGs, and I am a RPG addict) myself.