I've made a list of my favorite movies of all time before as well.
I am positive I will always end up leaving shit out, but how I tackled this list was browsing through my ratings on Letterboxd.com since I started using it, looking at previous lists I've made, and looking at the DVDs I own as well as other similar lists for things I may have forgotten.
I actually had like 75 movies that I had to narrow down to 50 and had to omit a few things I would've liked to keep, like Spirited Away.
But also I have a real dumb long memory span of things nobody else cares about, like my favorite movies.
Paris, Texas will always be the best movie.