Klonoa 2 was only mentioned once, so I might as well say it again. Adorable little 2.5D platformer. I like the first one more, but the sequel is still good. It's soft, bright, and colourful. Bit on the short side and maybe a little easy depending on how quickly you catch on, but still fun.
Pretty much all of the others I would mention you've already played or other people have said. I vouch for Okami, Ico, and Shadow Of The Colossus. However, Ico and SOTC will be coming onto the PS3 in a few months so you can buy it there if you want the HD. Ico might be a touch pricey or hard to find, but people might be selling it with the collection coming out. Beyond Good & Evil was also on the PS2 (among other platforms) and it too was re-released for HD. Never played it but it looks fascinating. But we're naturally not talking about the PS3 so I'll just shut my yap about the re-releases.
I love my PS2. In that generation if you wanted quality platformers, Sony had just the ticket *strokes her Ratchet, Jak, and Sly games*.
