There are relatively weak fan theories about a few SH games claiming that the protag was killing people in SH the whole time, hallucinating or what have you. However, as I say they are weak. SH3 is well know for the line from Vincent - "they look like monsters to you?". But dude has evil intent - what Heather is seeing in REAL in Silent Hill, and he sees the same. My take in that while they are clearly grotesque creatures, he doesn't see them as "monsters" in a negative sense as the term implies. Many cult members in the series see them as saviours or similar, actively praying to them.