This might be an animation-related question and you guys would have to think of any, but I will tell you this:

What is the most powerful opening scene ever to resonate even in animation history past and present?

Anyone?

if not the first (place) then the lion king opening is certainly one of the most powerful, and set the stone for many similar openings/scenes (not counting obvious parodies)

X-Men (90's) --> X Men Opening Theme (High Quality) - YouTube (http://youtu.be/sAkL2-vh2Sk)

I don't know that many animation films, but I'd agree with The Lion King. Reason might be that I saw it in theatres as a kid and back then cinema still felt mysterious and cool. Same goes for Aladdin. Both epic opening scenes.

If the whole of Finding Nemo was an opening scene, I'd name that one too.