Well, I've played all of the last generation PoP games, and I must say this one is both weaker and stronger. I also played Okami, and I've played Assassin's Creed.
For one, the element of Okami, the beautiful graphics, are worth the play all on their own. The contrast between pure and corrupted highlights the cel- shaded graphics that were beautiful in previous generations and are only that much better in high definition. You almost want to cleanse each area just to see the crisp, sharp shadows from the shining sun.