I'd love a prequel. A sequel doesn't really work because all the characters are dead and everything kind of wraped up. You don't have to worry about cast members returning either, because they would all be played by different, younger actors.

A prequel showing Junior, Johnny Boy, DeMeo, Feech and Dickie running things while Tony, Ralph, Silvio, Jackie, Pussy, Tony B etc. moving up in the family would be awesome. Add Paulie (whose kind of inbetween generations) and a young Chris (before he became a mobster) and you'd have an awesome prequel. I don't think it would all fit in a movie, so maybe a show or mini-seires would be better.

"I die outside; I die in jail. It don't matter to me," -John Franzese