So I just went through the 1,842 films I've seen and gave a 0-5 star rating on Letterboxd, and the only 5-star reviews I gave were for:
The Long Day Closes (1992)
The Color of Pomegranates (1968)
The Passion of Joan of Arc (1928)
Man with a Movie Camera (1929)
Loving Vincent (2017)
There are probably a handful of films I'd call perfect in their own right, but they don't necessarily overlap with those 5-star reviews. With the stars, and the logic behind that mode of rating, its a combination of stuff like: how important is this film in the evolution of my appreciation of the artform? how deeply did this film resonate with me? do what degree could I discern mastery or innovation of the artform? etc.
Nothing too systematic, I just went through over the last two days and gave a kneejerk rating to all of these, kinda just wanted to see what the spread would look like if I did it in so purely an instinctual manner.