Just got back from seeing Insidious, and have to say, is easily one of the best horror (horror, not slasher or gorefest, but actual classic horror) that I have seen in awhile. While there is some similiarities to the paranormal activites, and to a lesser degree Dead silence, it plays true to the more classical supernatural/spirtual horror.
What really got me though, was how many things in the movie made me think of Shadowrun. Spoilers so I can describe what I mean without ruining it for people who haven't seen it yet.
[ Spoiler ]
The whole astral travel concept. While I know this isn't something that was created for Shadowrun, and is part of a large number of religious/spiritual beliefs, the way it is presented is pretty damn spot on to the SR interpretation to it, without the whole magic angle. Aswell the travellers body being an empty vessel ripe for possession angle.
The spirits trying to steal the boys, and later the fathers body are essentially shadow spirits of different types and forces. Red face could easily be wraith while the old lady a nightmare
The Further, a place that human spirits aren't meant to be in and is essentially anaethema to them. Populated with the worst of the demons and body snatchers. Sound kinda like the deep realms, both the hive and the realm of the shedim.
The red faced man/demon if not a shadow spirit is easily a horror/master shedim
Reference to the Nether and netherwalking several times in the movie.