Perhaps the most unique emotion is experienced when this feature ends. I call the emotion "unique" because I have not come across such a feeling in any other movie or novel.
Here we have an artist performing song and dance his whole life. He has been at the very top of his profession for a lot of his career. He is a performing artist having fun all his life, all his performances are merely entertainment. I watched the movie thinking, "Here we have another feel-good musical movie.". Then the profundity of the climax came along. Just when I thought the movie will finish with Cagney receiving some award, the screenplay made me experience Cagney's realization of his accomplishment. The song and music he was just having fun with, had inspired an entire nation. Cagney suddenly realized he has lived a great life. In other such movies we know we are watching the story of a great man, sometimes the character's dialogues are written with gravitas. All through such films the character believes in his greatness being realized. Here Cagney realizes this only at the end of the feature, when he is at a very ripe age. Perhaps he wasn't even striving for greatness, he only understands his greatness as we approach the film's climax.