My perfect 10 list changes over time.
15 years ago I would have listed the cartoon version of the Hobbit. This was before I ever read LOTR. It's what got me hooked on Tolkien.
Butch Cassidy and the Sundance Kid is a little better than The Sting, but both are tens.
Pretty much everything in the last 30 years everyone has mentioned.
What I find interesting are the number of films people are listing that they saw in film classes. There are standard films that are shown to film classes like The Cabinet of Dr. Caligari, Duck Soup, Battleship Potempkin, and Metropolis, but I don't rank any of them as a ten. That's not saying that they aren't ground breaking and good films (except Caligari which I despised), I just wouldn't rank them as 10's.
And, so you don't think I only like movies from the last thirty years, my favorite's include Casablanca, Rear Window, The Maltese Falcon, Bridge on the River Kwai, Abbott and Costello Meet Frankenstein, Seven Samurai, Rashomon, Gold Rush, and many more, all 10's. And yes, some of these movies I saw for the first time in a film class. That's why I took it.