Why is Hamlet called a great tragedy?

"Hamlet" is a great tragedy because nothing seems to be positive in the story.  Hamlet is well written and is a conflicting character.  He changes moods often, speaks to himself in different manners indicative of his anger, depression, and moods.  The story involves murder and betrayal. The story begins with the murder of his father and his father’s ghost calling out for revenge.  Though Hamlet may be a hero to some, he has no friends.  Hamlet does not have a good relationship with women.  Hamlet rejects Ophelia and after her father's death, Ophelia takes her own life.  The story is one of revenge and deep thought and emotion.  Revenge only leads to many deaths of the father's and sons in the book.  There is no one in the story who actually finds any happiness.  Therefore, "Hamlet" is a tragedy.