It looks cool. It is amazing what you can do with some mannequins, a shit load of plastic wrap and some CGI. Some of the monsters are even things you really wouldn't want to run into in a dark alley. Hell you wouldn't even, in real life, want to spend the night with one of the props in your house.
The acting, for the most part, isn't terrible. When you have vaguely ridiculous dialog having actors who can say it with a straight face really helps. It is even better if they can RANT it with a straight face (can you say "Malcolm McDowell"?).
It is almost possible to hear the director asking (during the few hours McDowell was on set); "Mr. McDowell? Can you dial it up to a 9 on the crazy-o-meter?"
It never slows down to such a crawl that you have an uncontrollable desire to play Angry Birds during the film.
Likewise they don't spend too much time with explaining what is going on or on any back story of any sort. Maybe one in fifty horror movies manage to do that sort of thing well and it is just a guess that, had they tried it, Silent Hill Revelation wouldn't be one of them.
It never tries to be too clever, there is no fake ending hiding another fake ending hiding another fake ending. It just sort of slogs along without much reason to hate it or like it. Hell, it might even be better if you just edited out the entire plot and had monsters and insane asylum inmates and demons and crumbling walls all happening for no reason whatever.
If they make another Silent Hill film they should definitely get Terrence Malick to direct.