Hard to choose

It's between The Little Mermaid, Aladdin and The Lion King
The Little Mermaid : I absolutely love this one : the songs, the villain, the story...
Beauty and the Beast : I love it, there's too many songs but I love the story and Belle is one of the best Disney Princess.
Aladdin : It has been one of my favorite since I'm a child

Genie makes the all movie
The Lion King : The one that made everyone cry

This one is really deep, powerful and maybe the most "relevant" of the list.
Pocahontas : One of my favorite when I was a child... Now it's ok but I think it's a bit less memorable than the others.
The Hunchback of Notre Dame : The darkest Disney Classic

Visually it's wonderful

The story is great but it's a bit weird to turn a classic novel into this

If you don't pay attention to this, this is a major movie tho.
Hercules : It's funny but not Disney worthy!!!
Mulan : Nice... But not a big fan.
Tarzan : Loved it when I was 7-8... Not fan anymore.
So I go for The Little Mermaid.