Is strangers a remake of Ils (Them) ?
No. They're just rather similar. The Strangers is by some way the better film though.
In the mouth of madness
Prince of darkness
These gems do need a bit more mainstream love, but rest assured they are highly regarded in horror film circles.
btw - Silent Hill. Some visually arresting moments and a nice creepy feel to it at times. Shame I couldn't make head nor tail of the plot.