Forgive me for having played Battlefield 2: Modern Combat and not Parasite Eve. I cannot detail to you how the upcoming PSP game The 3rd Birthday builds upon the latter. But I can say how wonderfully it echoes the former.
The 3rd Birthday is a PSP adaptation of a Square Enix game originally released for Japanese cell phones. It now comes to American PSPs in early 2011, following up on Parasite Eve by pitting protagonist Aya against some sort of evil monster infestation that's wrecking New York.