all depends
if you like the old Universal Classics any of those are a hoot
the hammer films from the 60 to early 80s are also great fun
for bonafide scary films i would choose The Changeling with George C Scott
i watch as many horror flicks as i can in October but reserve Halloween and Halloween 2 for the day before and day of Halloween depending on where it falls
And Far far better than II.
Dark Night of the Scarecrow
Don’t be afraid of the dark
Trilogy of Terror