In no particular order, the more 'serious' ones:
The Exorcist (1973)
The Thing (1981)
Night of the Living Dead
Dawn of the Dead
In the Mouth of Madness
They Live
Halloween
Definitely almost all Stephen King movies. (Christine, Cujo, It, Carrie, Pet Cemetery. Go for the oldies not the new stuff.)
The Evil Dead series.
Friday the 13th
Hellraiser (The first few are good. Not so much the rest of the series, imo.)
Scanners
Reanimator
The Fly
Suspiria (1997)
Ginger Snaps (It has a bit of good comedy, but I would consider it mostly serious. Best werewolf movie Ive seen so far.)
The Descent (The sequel kinda sucks.)
Campy. Movies fun to watch, just as good in their own way:
Dead Alive
Chopping Mall
Killer Klowns from Outer Space (Beloved classic of "so bad its good" movies.)
The Attack of the Killer Tomatoes
Frankenhooker
Night of the Creeps
Zombeavers
Critters
As for the Silent Hill movie, it's mid in my opinion. You are better off watching a youtube video of the cutscenes and gameplay. If you do, watch Silent Hill 1~ The Room. I don't recommend anything beyond that.