yeah, i thought about that one myself as well. Although, in the end of the trailer for 3 it seems PH is returning.
the scene where he's dragging Heather at the end
Also there's two pyramid heads...
I initially thought it was his guilt, that Silent Hill was feeding off of.. it is in part. Above all else though, it seems to be his fear and despair that Silent Hill feeds off of the most. For Harry it was the same, except he was more of a pawn in a scheme. His situation was different, but more importantly his perception of SH was alot more wicked than that of James.
It's as if Silent Hill's alternate reality, was more similar to James' own reality.. he was already broken down, even before entering Silent Hill. Harry on the otherhand, he seemed like a character with more of a strong will. Silent Hill had to really pull out all it's tricks to break him down.