If you watch movies the way you look at paintings, this one deserves its reputation as a classic. As noted in the synopsis, the cinematography is brilliant for its time, the sets are an excellent example of German Expressism intersecting with reality, and it all looks just splendid. The trouble is, if you watch movies the way almost everybody does, there's rather a lot wrong with it.
Firstly, this is a 90-minute film with maybe 30 minutes' worth of plot, so almost everything goes on for too long or happens very slowly, and the pace is mostly glacial. When the hero loses a coat-button, the camera draws our attention to this seemingly trivial detail. Will this be an important plot-point? No! It happens so that a later scene in which he puts on his coat can be stretched by having his wife notice the missing button, search in her sewing-basket until she finds one that matches, and sew it on in real time.
Then there's the tone. Tragicomedy is a difficult blend to get right, and here they get it very wrong indeed. The mood simply changes abruptly every so often, as if the script was written by a tag-team wearing happy and sad masks. One very sudden mood-swing is so extreme that it's preceded by an intertitle admitting that the following turn of events would be ludicrously implausible in real life, but the author of this story has taken pity on his fictional character and thrown in an outrageous coincidence.
And of course there's Emil Jannings. Actors in silent movies by definition couldn't talk, so of course they all overacted. But this isn't just hamming it up; this is an explosion in a bacon factory! See Emil Jannings pull funny faces and comical capers as a slightly absurd but lovable old man! (You may find him more lovable if you don't know he later became an enthusiastic Nazi - oops, I just told you.) Now see him reel in bug-eyed horror as his world collapses! And now we've found an excuse for him to do a lengthy and irrelevant bit of drunk acting! Uh-oh, it's time for his descent into complete and utter despair! See the multi-faceted Emil portray near-catatonic depths of misery by impersonating Quasimodo in slow motion for half an hour! Is there no end to the man's talents!? (Actually, there is. Eating anything larger than a grape without getting some of it caught in his extravagant facial hair is completely beyond his capabilities.)
This movie is technically very good indeed, but it's also very old-fashioned indeed, in the worst possible way. And for a film which is supposed to be about 50% comedy, it's distinctly lacking in actual humor.