*in The Soprano's and Goodfellas:

Lorraine Bracco, Michael Imperioli, Vincent Pastore, Frank Pellegrino, Suzanne Shepherd, Tony Sirico

*in The Soprano's and Casino:

Steve Schirripa

*in The Soprano's and The Godfather:

Dominic Chianese

*in The Soprano's and Gotti:

Dominic Chianese, Vincent Pastore, Frank Pellegrino and Tony Sirico

*in The Soprano's and Witness to the mob:

Michael Imperioli, Kathrine Narducci, Vincent Pastore, Tony Sirico

*therefor, in Gotti and Witness to the mob, two movies with the same story:

Vincent Pastore, Tony Sirico and Frank Vincent, who's also in Goodfellas and Casino

*other people in Goodfellas and Casino:

Robert DeNiro, Joe Pesci, Frank Adonis, Joseph Bono, Clem Caserta, Daniel P.Conte, Paul Herman, Ronald Maccone, John Manca, Melissa Prophet, Mama Scorsese (Catherine), Charles Scorsese, Philip Suriano and Jerry Vale

it can't get more complete than this...