How anyone can say that this game is the weakest of the Silent Hill series, or weak in any aspect is at all is beyond me. This game is simply breathtaking. The environments, music, sound effects, monsters, storyline and appearance of this game FAR surpass any of the (admittedly excellent) previous 3 Silent Hill titles.
"The Room" just does it for me. I have played it at least a dozen times and it has been well over a year since its release. Right now just talking about it makes me want to play it again.
I personally feel, (in reference to what others have said about it) that it is the strongest in the series so far, with Silent Hill 3 coming a close 2nd, the 1st installment coming in 3rd and the "not very scary" but still very good Silent Hill 2 last on my list.
It is a big step away from the other games but thats what was needed. It would be too much to have 4 games that follow the same formula. Silent hill 4 has freshened up the series and more than opened the road for a 5th game on the upcoming PS3.
In conclusion - if David Lynch made a video game, this would be it. I can't think of a more glowing compliment for a game.