When I think of the "10 Greatest" films, I think of films that made folks think, and maybe even started a cultural or social transformation. No, they're not all my favorites, and some of 'em did nothing for me, necessarily, but history says they're significant (I guess):

Of Mice and Men
To Kill a Mockingbird
Inherit the Wind
Lawrence of Arabia
Easy Rider
One Flew Over the Cuckoo's Nest
Star Wars
Die Hard (hey, it started the action films!)
Raiders of the Lost Ark
Schindler's List

I could have mentioned Saturday Night Fever, but I purposely didn't...disco still sucks!