This is a movie you either love or hate, and I love it!
I've noticed people who love a game often hate the movie adaptations because they don't exactly match the game experience, but this is silly, if the movie exactly matched a video game than it simply wouldn't work, it wouldn't make any sense to anyone who didn't know the game, and would those who know it really well really pay to see nothing but a play through of it using real actors!? What would be the point, and in this instance, it probably wouldn't get a certificate!
I would say this movie is certainly one of the most thoughtful interpretations of a video game that I've yet seen, and is for the most part very faithful to the feel of the original games indeed, with only alterations of names of places and characters but with pretty much all of the original themes and overall spirit kept intact, and the treatment of the Silent Hill creatures is fantastic, especially when you know that they are in fact costumes and NOT, as most folks think, pure CGI, although some were 'enhanced' with digital effects such as the burning children who turn to ash (bit tricky to do for real).
The other reason why many people don't like this movie is because it requires thought!
You do have to listen and think to 'get' this movie, it has quite a complex plot that may require at least two watches before you get it all in your head and work it all out.
I don't think you need to know the games to understand what's going on, but it would definitely help, otherwise some speculation is required, hence the repeated viewing which makes it good value for home ownership.
The extras are great too, and I've lost count of how many times I've watched it now, but I'll be watching it again!
So, if you're looking for a brain dead gory horror movie that follows a simple well known formula or are a purist of the original games, you will hate this, however, if you're looking for a weird and freeky psychological movie with bizarre monsters that gets the blood pumping and brain pulsing a bit, buy this!