it's tough to say which is the best Disney movie cos it's subjective, they have so many outstanding ones. I basically grew up in the golden era of Walt Disney, and have a certain nostalgia and fondness for almost every Disney movie that came out in the 90s.
My fave is Aladdin, hands down. If it's on tv, I can sit down and watch the whole thing and not get bored, even after all these years. The animation effects at the time (early 90s) were groundbreaking and Robin Williams's characterization of Genie lifted the movie to a whole other level.
Also, the OST for Aladdin still remains my fave out of the Disney catalogue, fun, catchy and full of pomp. Nowadays, contemporary Disney Pixar theme songs are very bland and predictable and simply not memorable, def not up to the standard of the Disney classics, like A Whole New World, Under the Sea, Circle of Life, Beauty & the Beast.
Close 2nd is The Emperor's New Groove, watched it at least 7x and each viewing never fails to make me laugh. Disney went off tangent with this gem and it's the wittiest, most off-beat feature-length animation that's ever come out of there. The chemistry and banter btw Spade and Goodman is amazing, so freakin quoteworthy
(Sorry for the long paragraph, i can get carried away when it comes to film