I believe that there are 2 'generations' of animated Disney movies.
The first generation starts with Snow White in 1937 and goes through The Brave Little Toaster in 1987.
In 1988, Oliver and Company came out. This was Disney's first movie of it's new generation. While it wasn't a bad film, it was Disney's first foray into it's new direction on movies. Disney wouldn't really hit it hard until it's next animated movie in 1989. The Little Mermaid.
In my mind, something really changed with the Little Mermaid. I'll be honest and say that I am not exactly sure what it was. Perhaps it was just that I hit an age when I started seeing the movies differently, but I really think that something started changing with animated Disney movies at that point. Don't get me wrong, I like many of the new Disney movies. They just feel different.
So, my favorite of the 1st Gen Disney flicks is a tie, between the Fox and the Hound and Robin Hood.
My favorite of the 2nd Gen of Disney movies is, hands down, Beauty and the Beast.
There now seems to be a 3rd generation that has emerged, starting with Toy Story. Even if you don't think that there is a big enough difference between the first two generations to make a split, the differences started with Toy Story are hard to argue with. The characters themselves don't sing, it looks much less hand drawn, and it has a very intentional appeal to adults.
Mostly, I think all this has happened as the children who grew up with cartoons in general and Disney cartoons in specific became adults. There is now a market for more mature cartoons. I think The Simpsons, Family Guy, and Cartoon Network have proven that. The issue that I have now is actually an issue I have viewing a lot of older movies: I judge them by today's standards. The older cartoons were traditionally drawn and relied mainly on story. They are excellent films and well done, but I'm used to computer-assisted drawing and vast musical numbers. So I go back and watch Pinocchio and it doesn't have quite the same enjoyment as it did when I was a kid.
So, I am determined to show my kids the Disney movies, starting with the older ones and moving forward. Hopefully this will help them appreciate them for what they are rather than being jaded by the technological marvels we have now.
I plan to show the Star Wars sextet in the order they were released as well, but that's a different story.