This is a really interesting conversation, but I gotta ask... are we talking "classic" in the sense of meaning a highly critically-acclaimed work, or something that becomes an immediate box office hit and center of public conversation? Keep in mind they're not the same thing. Fantasia and Pinocchio were the former and not the latter; The Lorax and Ice Age III were the latter and not the former. Or are we talking both?
Couple of points:
First, I wouldn't cut the "Golden Age" off cold-turkey after 1994's Lion King.
Mulan and
Tarzan both have scores on Rotten Tomatoes comparable to those of
Lion King and
Little Mermaid, and were pretty strong box-office winners in their own right. The problem with both of these and other animated movies of the late 90s/early 00s is that they had to share the limelight with the new guys on the field, Pixar and post-CGI Dreamworks. Don't forget that the buzz around CGI was very, very high in the initial years after Toy Story (which, at 1995, came out right after the Lion King), and even masterfully-painted animated epics like Tarzan had a hard time competing with the CGI spectacles of Toy Story 2 and Phantom Menace.
Which brings the discussion of "classic" to its second conundrum: getting the public to acknowledge something that is high-quality. A lot of the buzz surrounding "great" movies is just that: buzz. Making a movie that you want to be a classic isn't as simple as finding a good idea and throwing a ton of money and talent at it. There are animators that believe Disney is on the best streak of high-quality since the 1990s, with movies like Princess and the Frog, Winnie-the-Pooh (91% on RottenTomatoes... that's right, 91%), and, yes Tangled. But if you were to ask the $7 million of people that went to see Pooh on opening weekend, you would never get that impression. Even Princess and the Frog had a soft opening at $27 million, and that movie easily could stand side-by-side with Aladdin or Little Mermaid on a musical, narrative, or artistic level. I think if P&tF had come out between Beauty and the Beast and Aladdin, it would easily be as fondly remembered as any of the other '90s films. A lot of it is just timing and finding the right audience at the right time.
I guess that brings me to another point: changing audience tastes. A lot of people loved the Pixar classics in part
because they rejected the Disney staples of musical movies with wacky sidekicks and mustachioed villains. I think people were getting a little tired of Disney's "formula", and that's partially why audiences laughed so hard at Shrek's jabs at Disney movies. In other words, when Pixar and Shrek filled in the "demand" audiences had for a new kind of animated movie, they became the new classics.
So in other words, there really isn't a formula per se for making an insta-classic. That IMO is why Lasseter has such fondness for quirky concepts and unusual situations in movies (and you can see his fingerprints all over the upcoming Reboot Ralph) - because if anything, it's the newness and freshness of a movie that makes a movie the most memorable. The problem is that is a very high-risk strategy for making movies, and the public can just as likely reject what they see as unfamiliar. And it also doesn't bode well for those wishing Disney would make Little Mermaids and Aladdins over and over.
Sorry, this post got really out of hand...