I agree 100% with Tony. I thought Richard Conte played Barzini in perfect accord with the novel. Puzo makes a point of portraying Barzini as a "modern Don," with little of the warmth of the older Dons, whom he dismisses as so many Moustache Petes. Barzini "was even rumored to have a toe-hold on Wall Street." In the film, notice in the Dons' meeting scene that he's the only Don who's smoking a cigarette, not a cigar.