I hated the ending at the time but over the years I came to accept it as a statement about his future.
It also left open the possibility of a movie or a sequel but unfortunately he passed away in real life.
Without question the worst finale and the biggest betrayal of fans who followed a beloved story for years was the final episode of St. Elsewhere.
I would place Lost as second in terms of a finale letdown.
St. Elsewhere was a good series.
David Chase said that that ending scene was one of the first things he fleshed out when he started writing The Sopranos, he knew from the beginning that was how he wanted to end it.