Here they are. My top 30. I have a bugbear about the term "greatest" as that's what people use alot to descrbe what they like. So this list doesn't include great fims like Schindler's list, The Good, the Bad and the Ugly and the Godfather. Because although they can be considered some of the Greatest films ever made, they are not the films that I would necesarily want to watch over and over again.
Jaws
Timecrimes
Alien
Mississippi Burning
Amelie
Enemy
Saving private ryan
Oldboy
12 angry men
Blue Valentine
The road
Animal kingdom
Arlington road
2001 a space odyssey
Pulp Fiction
star wars iv: a new hope
A tale of two sisters
Fargo
Memento
Casablanca
Boyhood
I saw the devil
The sure thing
Martha marcy may marlene
500 days of summer
Moon
Dead Man's Shoes
American Beauty
Full Metal Jacket
Papillon
Jaws
Timecrimes
Alien
Mississippi Burning
Amelie
Enemy
Saving private ryan
Oldboy
12 angry men
Blue Valentine
The road
Animal kingdom
Arlington road
2001 a space odyssey
Pulp Fiction
star wars iv: a new hope
A tale of two sisters
Fargo
Memento
Casablanca
Boyhood
I saw the devil
The sure thing
Martha marcy may marlene
500 days of summer
Moon
Dead Man's Shoes
American Beauty
Full Metal Jacket
Papillon