The choice of music used in the show was flawless as well. From "Crystal Blue Persuasion" to "Baby Blue" the music was very well chosen.
Also, it had probably the perfect ending. Most great TV shows really flub the final episode. This one was pretty much perfect.
Second place on my list of best TV shows would go to "Mad Men". Probably because I work in Manhattan and can identify with much of the culture. My father would have been exactly Don Draper's age during the show and I remember visiting his workplace in the mid 1960s and it was just like that. Everybody smoked, had liquor in their offices and the secretaries were often a little wild and crazy. Really a good period piece and another show where you had to pay attention to each episode. And the music selection in that show was flawless as well. The only thing I didn't like that much about "Mad Men" was all the sex scenes. But my father confirmed that there was a lot of fooling around during that era.
Mad Men is very good. I started watching and I am somewhere midway now. Need to get back into it.