According to a PlayStation 3 owner, “you get more jaggies and artifacts when playing a PS2 or PSone game on the new console than if you were to play it on the PS2.” Video after the jump.
He says this is because the PS3 resizes the image at a low resolution with no filtering. I don’t know, I noticed the same issue once I started playing PS2 games on my 50-inch high-def television, they just look like crap on a big TV. I haven’t noticed a substantial difference between playing PS2 games on either system. Have you?