This shit ain't right, man. Not only is 51 too damn young, but it happened to too fine an actor.
Gandolfini was one of the finest and most criminally underrated actors in the American stable. He was so effective at conveying authentic emotion from his characters that he was often cast as heavies and villains where that kind of intensity was most demanded, but the skill that gave him that quality was one of the rarest kinds of talents you can find. The tragedy for those of us who are not his immediate friends and family is that we never got to see him given his due and allowed to branch out of the meathead-bully roles that he excelled in before and since The Sopranos. Thankfully, some wiser heads who knew what they had cast him in a number of unseen roles where he got to showcase his non-Tony Soprano side--John Turturro in Romance & Cigarettes being the most prominent, but also Gore Verbinski in The Mexican--but aside from some roles in underwhelming indie movies--with the exception of Not Fade Away--America as a whole never got to see the incredible range and heart he was capable of unleashing.
In my mind, Gandolfini's passing is the greatest loss of untapped dramatic potential since Vincent Price. Somewhere, in an alternate world, Vincent Price spent the late 40s to the 1990s doing evisceratingly clever dramatic work instead of schlocky horror films, but much like Gandolfini's ouevre post-2013 ouevre, that's a catalog of movies we'll never get to see and it pains me to think about the gaping hole it leaves in our culture.