Which is kind of a tricky question for me, since I'm really not a movie gal. But I do have some favorites (as with all these sorts of lists, in order by of which they came to mind, nothing more):
1. Robin Hood
Guys, I love this movie so much. The banter between Robin and Little John, the truly righteous anger of Friar Tuck, Sir Hiss always saying just the wrong thing, the music.... (Also, a story where there's no conflict between friendship and romantic love.) Watching this movie is like wrapping myself in a warm fuzzy blanket of happiness.
2. Muppet Treasure Island
Confession: this might be my favorite Muppets movie. My sister and I got it out from the library so many times that our parents finally caved and bought it, and when we started swapping out our VHS for DVDs, this was one of the first to get the upgrade. I can sing along to all of the songs, I can quote most of the dialog, and my family has so many in-jokes based on this movie it's a little nuts. Picking out just one scene to share here was really hard because there's so many that to this day make me giggle like a little girl.
3. Princess Bride
Guys, I don't think I can explain how important this movie is. It's foundational. This is the movie I bought a copy of specifically so I could take it to college with me, even though I was a penniless student carefully scraping together funds in preparation to pay off various loans. For long years, my sister and I could upon demand reenact this entire movie, scene by scene. We could probably still manage large pieces of it if prompted.
I have very fond memories of watching this with my mom when we both had terrible cases of the flu and managing to forget for an hour and a half just how miserable we felt. It actually hurt a little to laugh so much.
I went into this movie dubious and came out with my socks charmed off by it. There are fewer songs than most Disney movies, but they're all good ones, and Max vs. Flynn is a thing of joy to watch. Also, the main villain has actual motive for her actions besides just "I'm the villian".
6. O Brother, Where Art Thou?
Man, this is just a fabulous movie. Musically, visually, character-wise--not to mention all the references to the Odyssey, which make it even more fun than it would've already been on its own. (Also, definitely a movie that's worth getting the soundtrack for.)
Bonus: The Phantom
Very silly? Yes. Fun? Also yes. "Your dog's a wolf!" "I know." This is the other movie where my parents broke down and bought a copy because we just kept borrowing and reborrowing it from the library.