The best TV show of 2012 is HBO's Boardwalk Empire. Season 3 was absolutely wonderful and hit on all cylinders with 100 percent power. The acting, the writing, and directing were all impeccable this year and each week was like watching a mini film to be quite honest.
Steve Buscemi continues to be one of the most underrated actors of our time. Bobby Cannavale's Gyp Rosetti was truly one of the most frightening characters to every grace the small screen. And, like the previous two seasons, the historical context stayed true to the times. Prohibition was a horribly violent time and showed the folly of trying to outlaw alcohol.
Here's one of the trailers for Season 3.