QUICK EASY RULES:

There must be 31 films

6 countries

USA (The Exorcist)
France (Revenge)
South Korea (I Saw the Devil)
Denmark (The House That Jack Built)
Spain ([REC])
Japan (Cure)

8 decades

2020s: Nope (2022)
2010s: The Visit (2015)
2000s: Slither (2006)
1990s: Army of Darkness (1992)
1980s: Dressed to Kill (1980)
1970s: Messiah of Evil (1973)
1960s: The City of the Dead (1960)
1920s: The Unknown (1927)

2 insect centered films

Mimic
The Fly

1 horror film set in space or the future (relative to when it was released)

Event Horizon

2 animated films

Perfect Blue
Frankenweenie

1 bloodthirsty old person/people film

From Dusk Till Dawn

2 1970s regional US films (Thanks Sean Young)

Messiah of Evil
Shivers

The worst horror sequel from the 1990s that you haven't seen and can access. (I realize that this will take a little work)

Alien³

1 German Silent

The Cabinet of Dr. Caligari

5 Films from David Cronenberg, Ti West, Bill Rebane, Charles B. Pierce, William Grefe and/or Joy N. Houck Jr.

Rabid
M. Butterfly
Crimes of the Future
The Brood
Dead Ringers

2 Christopher Lee films

The Wicker Man
The City of the Dead

1 film with a musician or band in it (A real life musician or band)

Jacob’s Ladder

1 Stephen King adaptation that is not the first go around.

The Dead Zone

1 Lon Chaney film. (NOT JR)

The Unknown

And 1 Tobe Hooper Film (There must ALWAYS be a Hooper film)

The Texas Chainsaw Massacre 2