One thing I'm rather fond of in the Silent Hill games is that there is, at least usually, a good deal of interpretation that needs to be done to really get at the message of the games. Silent Hill 2 for instance does a very nice job of indirectly telling you an awful lot about the characters, and what's going on around them. There's one little notion buried in there that most people don't seem to pick up on though, and it's one of my personal favorites. The suggestion that, at least in the odd numbered games, you're hallucinating and murdering innocent people.
Now, I'm not saying that you have no grounding in these games. There are many things you just have to take at face value. For instance, there really is a creepy cult, they really are trying to bring their creepy monster god into the world, and their attempts to do so do seem to be causing some funky alternate rusty metal dimension to leak into reality. I'm just saying that when you're running around in a hospital caving in the skulls of twitchy freaks, you're actually murdering perfectly normal medical professionals. Here's why.
Let's start with Silent Hill 1. First off, Harry clearly isn't right in the head. Even by the standards of the series, he's... spacey. Frequent blackouts, explanations he gives don't even make sense to him, and when he follows his 5 year old daughter into an alley full of monsters and finds a note written in blood on her little sketch pad, he isn't at all concerned. Clearly there's something wrong with this person's mind.
Next we have the monsters themselves. On the one hand, in every Silent Hill game, we have monsters whose nature reflects the personal mental hangups of the character du jour. If you haven't picked up on that by this point, overanalyzing these games clearly isn't up your alley. However, particularly in the first game, they're also distorted versions of things which are appropriate to the setting. Weird little kids in the school, doctors and nurses in the hospital, dogs and such outside.
Here's where my theory first started to form. Look at HOW you kill monsters in these games. In the most violent games you'll see, you're still going to kill monsters in a pretty impersonal way. You might shoot'em in the head and have it explode, or hack them limb from limb, but you're going to be pretty impersonal about it. In the Silent Hill games though, let's face it, you flat out murder these things. Ideally, you'll turn off the lights, sneak up behind one of these freaks, pull out a rusty lead pipe and bash its skull in until it falls to the ground twitching, then kick it until it stops moving. Even if you run in with your flashlight on and they see you coming, it's a pretty darn visceral sight.
Now look at how THEY attack YOU. Especially in the hospital. One twitchy nurse comes up and holds you down. Another rushes up and stabs you in the arm with the knife she's carrying. That's not how you kill somebody really. Assume for a moment that you're hallucinating. These are normal human nurses, and those aren't knives, they're syringes full of sedatives. Look at how much more sense the animation of these attacks make now.
Speaking of nurses, remember Lisa there? You meet her in the hospital hiding under a table, her memory is somewhat screwed up? Now do you remember the last time you see her? She says she'd wandered around a bit and that she realized that she "wasn't different from everyone else around" or something to that effect. Then her appearance changes to match the twitchy freaks, although she isn't behaving in a threatening manner, and you run before she can come give you a hug. Going by my theory, this makes perfect sense. She realizes she's hallucinating to some degree, and that everyone is in fact perfectly normal. She attempts to explain this to you, obviously upset at the realization you've been murdering her coworkers, and your skewed view turns her into a monster as you misinterpret her. What's the alternative explanation here exactly? She was actually a twitchy hunchbacked bloody zombie who hit her head, thought she was a normal human, magically appeared as such, and was nice enough to explain this to you before attempting to eat your skin?
My final piece of evidence from the first game explains the why of things here pretty nicely. Over the course of the game, you find various little files, as is traditional for the genre. Most of these are totally utilitarian hints for puzzles, or handy info on the cult and what they're up to. Then there's some other files. Ones you pretty much have to encounter when going for the good endings, which discuss at length how pollen from flowers around the town is hallucinogenic, and thus used to synthesize drugs. Now, either this is the only unimportant information the game contains, thrown in for no reason other than to flesh out the number of files you find, or this is here to reinforce the premise I'm describing here.
Silent Hill 2 has no particular impact on my theory one way or the other. SH2 does its own thing when you get right down to it. The cult isn't a factor in anything that's going on, and we have this whole personalized guilt manifestation soul searching going on which doesn't factor in any of the others. Personally, I'd say SH2 is exempt here unless you can convince me otherwise, if only because being a mass murderer here would completely destroy the story of the game.
SH3 on the other hand is fully on board. Just a quick look at Heather's eyes and a listen to the title music brings drugs back into the picture if you want them, cult's back, and once again, the most aggressive action any of these monsters are taking is giving you a hug. More to the point, these monsters are decidedly passive. If you don't go out of your way to kill things (which incidently there's a special reward for) the vast majority of monsters will just sit around in the shadows watching you. I have plenty more than that to go on here though.
Halfway through the game, you find your father sitting in a chair, his brains having been blown out. Quite nasty. Shortly thereafter, this is revealed to be the work of a hit man, who you then fight in the form of some weird freaky spiky monster... who you would think would have used those speedy bladey arms to do any killing that needed doing, not a gun. Later, you meet someone else. Someone's father, who you've been talking to on the phone for some time. When you actually meet him, suddenly he's some freaky fishy monster you take down. Once again, someone who would by all other evidence be a normal human is a monster when you find yourself in a position to kill them.
Now for our final nail in the coffin, we have a little conversation towards the end of the game which validates this notion as much as can be hoped for while still keeping up appearances. While I don't remember it verbatim, it goes something like this. "You're a psycho." "Me? You're one to talk! I've seen the way you kill them, then smile while you grind your heel on their necks." "You mean those monsters?" "... They look like monsters to you?"
Silent Hill 4 has no bearing on this little theory of mine, having no real connection to anything, and leaving nothing to the imagination.