American Pop (1981).
Vastly underrated but well made and animated drama from Ralph Bakshi is perhaps his finest movie in my opinion. This is also his most mature as it doesn't go overboard on the sex and violence routine but more human drama on characterization and some war/gangster violence. The plot deals with the generations of a Jewish Russian American family from Vaudeville to the early 90's in that "Forrest Gump" kind of history in one film way.
It's funny, sad, drawn nicely with rotoscoping and sometimes fun with a great soundtrack from the 1900's to the 1980s. Anyone who enjoyed "Waltz with Bahier", "Grave of the Fireflies", and "Pink Floyd The Wall" in terms of mature animated features should check this out.