While it is not a crazy popular attraction, Walt Disney: One Man's Dream is a standout for me, and should be for any true Disney fan.
The attraction does a great job of showing you Walt's dream from start to present. Disney's dream will never be complete, and this attraction does a great job of showing that.
From the unique ideas with EPCOT to the unique ideas that Disney had for animation, the attraction does a great job of showing where Walt's true genius came from.
Lastly, you get to view a film showing you Walt's personality and his charm that led to "the mouse" and the empire that is Disney. *Side note* I recommend checking out the DVD/video "Man Behind the Myth" for an even deeper look into Walt and his life.