(I think that I have the advantage of Burgess in the matter of Goethe: I can remember three or three and a half lines, probably somewhat mangled.)
There is something desperately wrong with our remembering mechanisms. The trivial, especially if it is in verse, sticks. Great thoughts and great expression of great thoughts vanish. I have repertory of about a thousand popular songs and only one line of Goethe. From one of the 'Little Tales' in Punch, I remember this: "He said I love you, and she said I love you too. Then they went in to tea and he made jokes about the jam sandwiches.' What the hell is wrong with us? The greatness of James Joyce lies partly in his recognition of the importance of the trivial, but it is not his responsibility to explain the importance. Flaubert's Felicite dies seeing a parrot flutter over her head. I shall die on the memory of the HP Sauce bottle from which I first learned French: 'Setty sauce, de premier choyks. . .'
I suspect that the sticking power of the trivial verse comes in part from the age at which it is encountered. The lyrics of John Lennon or John Denver are remembered because encountered in childhood or adolescence, ages of energy and hope. And I think that the same process works for much better verse. The Athenians captured at Syracuse could recite Euripides at great length; Eugenia Ginsburg, on the train to Siberia, could recite Pushkin for half an hour by the watch; I'm sure that they learned the verse young.