It's one of those lists everybody likes to make and debate. It's a marketing technique at music and DVD stores. Can one actually make such a list? Or do tastes change? If you look at the Oscars through history, some oscars are clearly better than others.
I don't think you can make one list - I think it has to be split by genre.
Here is mine. I've kept it to movies I've seen/remember. There are others I think I saw when I was a kid that I need to watch again - like "The French Connection," "Butch Cassidy And The Sundance Kid" and "The Good, The Bad And The Ugly" . I can hardly remember them now.
The following are not an attempt at a best 10 or 5. They are not ordered. They are merely the best as they came to mind. I will update them as I remember more.
Remains Of The Day
Room With A View
Pride and Prejudice (2005)
The Wall - Pink Floyd
As Good As It Gets
Best Bond Movies
For Your Eyes Only
Tomorrow Never Dies
The Bourne Supremacy
Indiana Jones and the Temple of Doom
The Last Boy Scout (probably not on too many "movie buff" lists, but it cracks me up)
The Godfather I
Dead Poets' Society
A Beautiful Mind
Requiem for a Dream
Stand By Me
Man on Fire
Silence Of The Lambs
Science Fiction / Fantasy / Superheroes
The Lord of The Rings - Return of The King
Star Wars - The Empire Strikes Back
A Fish Called Wanda
There's Something About Mary
A Bug's Life
(I have yet to see the Toy Story movies - difficult to believe, I know)