The Best in my eyes from my favorite directors go as follows:
Europa by Lars von Trier
Manhattan by Woody Allen
Viridiana by Luis Bunuel
Cries and Whispers by Ingmar Bergman
8 1/2 and La Dolce Vita are tied when it comes to Federico Fellini
Reservoir Dogs from Quentin Tarantino

O Brother Where Art Thou (2000)
Bonhoeffer (2003)
Pan's Labyrinth (2006)
Gojira (1954)
The Mission (1986)
Nosferatu (1922)

@Svidrigailov: I don't think I "got" Reservoir Dogs and found it really unfulfilling. Can you talk about it a little bit?

Heathers
Goodfellas
The Godfather
The Usual Suspects
The Shawshank Redemption

In no order:

Sabrina (Classic or remake)
The Quiet Man
Cinema Paradiso
Shawshank Redemption
V for Vendetta

@Celticfox: Aha! The Quiet Man! That's my grandfather's favorite movie! We got a DVD for him last Christmas. He can't really see, anymore, but he's got the movie memorized, so he knows what's going on the whole way through. "Now, cheer like you're Protestants!"

No Country For Old Men
The Godfather
The Iron Giant
LOTR
Office Space
Burn After Reading
District 9
Chicago

Oh! And Young Frankenstein. Almost forgot that one!

@Willtor Yes! It was one of the movies my father and I would watch together so it will always have a special place to me.

@Willtor Reservoir Dogs is in my opinion Quentin Tarantino's best depiction for human imperfection and emotion

In no particular order (after the first three, anyway):
Harakiri (1962 Kobayashi/Nakadai version)
There Will Be Blood
El Cid
Army of Shadows
Madness of King George
The Firm
Syriana
Alexander (the super-duper unlimited extended director's cut)
Watchmen
Der Untergang
Insomnia
The Ice Harvest
American Gangster
Blade Runner
Gattaca
Conan the Barbarian (for James Earl Jones' two speaking scenes alone - easily the most under-appreciated villain in the history of film)
The Lion in Winter (Peter O'Toole/Katherine Hepburn version)

No Country for Old Men would be on here, but the scene with the old men talking about cats complete ruined the movie for me.

In no particular order (excluding my favorite comedies for the time being, that list will require some more contemplation)

Black Hawk Down (2001)
Full Metal Jacket (1987)
Gran Torino (2008)
Rambo series (1982, 1985, 1988, 2008 respectively)
A Fistful of Dollars (1964)
Unforgiven (1992)
Hang 'Em High (1968)
Dirty Harry series (1971, 1973, 1976, 1983, 1988 respectively)
The Patriot (2000)
Batman trilogy (2005, 2008, 2012 respectively)
James Bond series (1962 - present)
Patton (1970)

American Gangster (2007)
3:10 to Yuma (2007)
The Right Stuff (1983)

The Shining 1980
District 9 2009?
Alien 1979

i too love Reservoir Dogs and pretty much everything Tarantino has done. I love True Romance.

In no particular order, some of my favorites:
Fight Club
In Brugge
Lion King
Nothing
The Outlaw Josey Wales
The man with no name Series
The Seven Samurai and Yojimbo
The Professional

Lawrence of Arabia
Godfather
Count of Monte Cristo
Star Wars , Ep. IV
Lion in Winter
Casablanca
Avalon (1990) --the one about immigrants, not King Arthur
The Fountain (Hugh Jackman)
O Brother, Where Art Thou?

Gladiator. It does everything a film should do.

As in, "Are you not entertained?"

For a fuller list:

Gladiator
West Side Story
Star Wars
Four Weddings and a Funeral
Beauty and the Beast
Pulp Fiction
Lagaan
Annie Hall
Life is Beautiful
The Silence of the Lambs
Schindler's List

Whenever I'm asked to pick top films, pieces of music, or literature, I always try to think in terms of:
1. what piece best represents that medium
2. pieces of work that that medium does better than anything else
3. pieces that best represent us if you had to give someone a crash course in how to understand humanity.

"Gladiator. It does everything a film should do."

That's why it's so predictable and boring.

(I will say, though, that the Germans' doomed struggle for freedom against the legions of the Roman imperialist aggressors in the opening scenes brings me to tears every time)

Lol Tolstoy: as if the films you picked don't comfortably fall in to the 'predictable' and 'boring' category?

There Will Be Blood
Alexander
Watchmen
Der Untergang
Insomnia
American Gangster
Conan the Barbarian

If Gladiator is as you describe, there is no way you can say that these films are not that as well.

Gladiator is amazing:
-every performance is acting superbly
-it looks beautiful: every scene is vibrant and breath-taking
-it helped pioneer film technology in terms of CGI
-its epic plot covers action, adventure, suspense, romance, comedy, drama, war: it is a true masala movie that has something of everything
-it is a perfect timeless story of an individual's struggle against fate and the corruption of power
-elements of history (with licence) to teach (partially) and inspire people to find out more
-base action but depth as well, in its tight script and challenging ideas about corruption, power, the human condition - the film aims probably as wide as possible in its audience reach.

The thing about movies is that you can be impacted by an outside event. First movie you ever made out in, might seem a lot better than if you'd struck out... Though you might not remember it all...

That said, 5 movies that affected my life in some way:
Star Wars: A New Hope
Dead Poet's Society
Good Will Hunting
The Muppet Movie
For Your Eyes Only

I love the opening scene from Manhattan with Gershwin playing in the background and Muriel Hemingway is fabulous.

The Graduate
Downfall
Hannah and Her Sisters
Borat
Goodfellas
Gattaca
An American Werewolf in London
North By Northwest
Fargo
The Godfather, Part II

There are many other films that could be candidates for my top 10. Ask me on another day and I will probably give you a different answer.

@NigeeBaby +1 I love the opening of Manhatten. Probably my favourite opening.

"He adored New York City. He idiolized it all out of proportion..."

*idolized

North by Northwest - although any Alfred Hitchcock is good
The Twelve Chairs and The Producers (original)- Mel Brooks before he went for even easier laughs
The Maltese Falcon - classic Bogart in film noir