Which Six Days is this?
Has the thread officially devolved into “some movies I really like a lot” or is there still some semblance of the OP’s question remaining?
I’m going to assume the latter, which is a really tough question. A perfect movie, like a perfect game in baseball, must have no missteps, no escapes. The directing, writing, casting, cinematography, and acting need to have no flaws.
That said:
Seven Samurai (Kurosawa, 1954) actually, one could make a list of 5 perfect Kurosawa films!
Children of Paradise (Les Enfants du Paradis, Carné, 1945)
Paris, Texas (Wenders, 1984)
Pulp Fiction (Tarantino, 1994)
The Godfather Part II (Coppola, 1974)
These aren’t the only perfect movies, but they are the ones that came to mind (Day for Night, Singing in the Rain, Logan, and many others). Going in, I thought that at least one 21st century movie would suggest itself, but I think for me there is a “test of time” that has to happen to separate perfection from just favorites.
It’s a 2017 Brit docudrama about the hostage taking at the Iranian embassy in London in 1980.
Major League
White Men Can’t Jump
Star Trek II - The Wrath of Khan
The Avengers
Deadpool
Which one?
The 1st one.
O.k., it is your opinion.
The Avengers (1998 film) - Wikipedia
Probably talking about the first Marvel Avengers movie. The one you linked to was far far from perfect. Many people don’t know it or remember it.
I certainly didn’t. I guess I should have googled for “other movies named The Avengers” before posting. Yes. I did mean the 1st Marvel Avengers movie.
Everyone knew what you meant.
I’m not a perceptive movie reviewer in this life, but:
Dr. Strangelove … (everybody dies)
Young Dr. Frankenstein (Blazing Saddles also but not perfect)
Rogue One (everybody dies)
The Fifth Element (I like everything about it, great performances, visuals, pacing, Bruce Willis winning the Oscar for most Bruce Willis evah.) So shoot me.
and … I’m thinking
Galaxy Quest over Airplane (same redemptive arc but more story than strung together gags)
Not so highbrow but perfect for me.
Just having a little fun. 
One more to add for now:
The Asphalt Jungle (1950) a perfect noir film
Not necessarily:
As I said, I prefer glorious messes to flawless films. The question can be answered with either.
Joe Vs. The Volcano The actors and director hated the film, but they are wrong. It’s absolutely perfect. The budget sets and disjointed dialogue just add to the outer worldly dreaminess of Joe’s condition. I have seen this over 15 times, the latest with my teenage son’s first viewing and not only does it hold up, I find new things to appreciate about it because I have changed since last seeing it. I don’t know another film that does that for me.
Nothing about this film is what it seems at first and the experience is richer for it.
This isn’t how I remember it…
I don’t know about this one. The fact that none of the guards or other prison personnel ever peeked behind the poster seems like a big flaw in the plot.
You’re right! I’m done thinking.
Rashomon (1950, Kurosawa)
The Thing (from Another World) (1951, Hawk/Nyby)
Charade (1963, Donen)
Jurassic Park (1993, Spielberg)
Field of Dreams (1989, Phil Alden Robinson) Okay, this last one is a movie I will watch just about anytime it is on and it is very likely I am using it because of my emotional response to the passing of James Earl Jones, but there it is.
My numbers 3 and 4 are Pulp Fiction and Shock Treatment.
Well in fairness, those guards hadn’t seen or read The Shawshank Redemption at the time, so they didn’t think of it.