Mmm... Honestly, I can't pick just one. I'd have to go with the original trilogy for Star Wars. Or hell, literally all the Star Wars movies. With the exception of Solo since I haven't seen that one yet.
Mine is between the Little Mermaid and the Lion King. I loved them both so much as a kid, and I still enjoy watching them. A Little Princess comes in close second though, another favorite of mine since I was young
It has to be Memoirs of a Geisha. I just can't get over how sad yet entertaining it is, atleast to me personally. There's just something that captivates me in the sad story of Sayuri.