Hmmmm..
Brokeback Mountain
Lord of the Rings trilogy (RotK, then FotR, then TTT)
Crouching Tiger, Hidden Dragon
The Wizard of Oz
Then some odd combination of things that might change depending on my mood. (Maybe Being John Malkovich, or maybe Spinal Tap, or maybe Thelma and Louise, or maybe something else I'm not thinking of at the moment.) The first four, though, I've bought on DVD, which says something.
I don't put any "classic movies" that I saw as an adult on my list, not because I don't like them, but because I've never seen them on a big screen, and my impressions of them are so completely influenced by knowing that they are "Great Movies" that I don't know if I can judge them fairly. (I saw The Wizard of Oz on a big screen when I was a small child, though, and loved it. And my Inner Five-Year-Old refuses to let anything else take its place on my top 5 list, although she grudgingly accepts that I prefer some other movies now.)