If you can pin an oversimplified theme to the GF Trilogy, it's "Crime Doesn't Pay." Michael became the most powerful gangster in America--probably in the world--and yet, as the last scene shows, he lost every single thing he loved.
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.