This is going to be a very short review because even if I wanted to give specific examples of why Silent Hill was so excruciatingly bad, I couldn't. It was so bad that even as I was watching it, I was forgetting it. But even though it was the Memento of movie-watching experiences, I'll make an attempt to illustrate with a few things I do remember.
Something happened in a town 30 years ago (or 25...ish?). There's a girl who was burned in a fire, something about unresolved mother-issues, an orphanage, the ashes that never stop falling, a sexy, therefore unrealistic, dykish cop in tight leather pants who I hoped would have a hot girl-on-girl "we're in grave danger and might die at any moment so let's take this last life-affirming opportunity and fuck!" scene(s) with the lead chick (actress Radha Mitchell) but of course it never happened. There was sexy mutant zombie nurses who all had hot bodies and nice racks who looked like they might break into Michael Jackson's Thriller video dance at any moment (I wish! I love that part of the video!). There was a creepy orphan girl who played a demon who had to say some pretty fucked-up, demonic lines. In fact, I have a big issue about child actors who have to say fucked-up lines and play fucked-up roles in general.
RANT: All I kept thinking was "what kind of mother would let a child say the lines the girl in the movie had to say - acting or not, they would have a negative, even nightmarish, effect on her." Hello bad parents of child actors out there! It does affect your kid to say fucked-up lines and play fucked-up roles. But you say, "Oh, my son/daughter is really intelligent and they know it's just make believe." Wrong. You are a bad parent desperate for your child to snag any role so you can live off the fat of their success some day. Period. Paging Linda Blair! OK, rant over.
To continue - there was a demon and really lame and obvious references to the good ol' Salem witch trials and whatnot - been there done that. And the woman who played the Borg queen in the later Star Trek movies. Oh, and Boromir. And I didn't know this movie was based on a video game. Wait - let me see if that changes anything. Hmm. Thinking about that...based on a video game. Nope. Changes nothing.
That's all I can really tell you. The script was written so poorly, the plot so convoluted, and the climax so laughable that I lost a little of my soul after having sat through such crap. If fact, sitting in crap might have been more interesting than Silent Hill.