Nightmare on Elm Street series (1, 3, and 7 are the best), Halloween, and Child's Play.
If you're looking for more modern one's that are on Netflix try The Babadook, You're Next, The Taking of Deborah Logan, or The Den
Perfect Blue
Night of the Living Dead (1968)
[REC]
Alien
The Thing
Midori (1992)
Braindead
Tetsuo: The Iron Man
Suspiria
The Texas Chain Saw Massacre
Inland Empire
Videodrome
A lot of people say "House of 1000 corpses" is disturbing but I didn't find it that disturbing but it isn't scary at all! I don't even think it's suppose to be scary.
The Ring
The Grudge
The Haunting in Connecticut
Sinister
[REC]
Carrie
The Silence of the Lambs
The Babadook
A Tale of Two Sisters
Not really "horror movies", but I also recommend:
Se7en
Pan's Labyrinth
Funny Games