Hugo is a stealth hagiography of
Georges Méliès. Which I am 100% okay with, because it's the hagiography Méliès deserves.
The whole thing is just a way of tricking theater audiences into learning about early, great film history. There's truly just a part of the movie which is SURPRISE HISTORY LESSON, but it's a montage of great early film sequences (with the interesting omission of Odessa Steps, now that I think about it), so they're images that people kind of deserve to see.
There are segments of the film that I think Scorsese included simply for the pleasure of being able to duplicate, shot-for-shot, sequences of Méliès films. (That, or so he could have a duplicate of the Man in the Moon from
A Trip to the Moon hanging over his fireplace.) But it's a joy to see something like those films in modern definition and color, so it's kind of a universal boon.
Of course, all the bits that aren't about Méliès are pretty good, too! (Mr. Cohen is a particular delight.) My only real complaint is that it runs a little bit long, but honestly? It's really worth seeing.