I'm going to say Silent Hill because the concept is still pretty strong and easy to do stuff with if given to the right people.

MGS pretty much ended on a high note for me, so I'm pretty content to let sleeping (diamond) dogs lie. Castlevania would be my second choice, but I also feel like the the Indy Game community has me covered on that front.

I would also love to get Suikoden, but I would want the creator to work on it (at least as an advisor) but I'm not sure if the series could be properly resurrected in a way that would make me happy.