The Victims of Communism Memorial Foundation has published the results of a survey indicating that a significant segment of those born since the fall of the Berlin Wall have not been served well by their education in the history of the 20th century.
From the survey:
The error with respect to Hitler and Stalin may be more understandable since Stalin had about ten more years to do his killing. Given time Hitler may well have exceeded Stalin's butchery. That is the generous interpretation.
Victims of Communism Memorial Foundation: Annual Report on U.S. Attitudes towards Socialism (pdf)