For better or for worse (I say for worse because it's become a cliche now), this was the series that paved the way for so-called "villain antagonist" series like Breaking Bad, Weeds, The Shield, Hannibal, etc. where characters who would have been considered villains in "traditional" TV series are made out to be the heroes and the people to root for. It was a great novelty and shows like Breaking Bad showed how well it could be done, but it's become a bit of a storytelling cliche of late. But when The Sopranos came along (or The Sopornos as my parents called it because of its sexual content), it blew the doors off.