Boardwalk Empire (HBO, Sundays, 9 p.m. E.T.), the best new drama of the year, is the sweeping birth story of that myth, centering on Thompson (Steve Buscemi), the man who kept Atlantic City wet. It's also HBO's return to the field of big-budget, big-idea dramas it dominated in the Sopranos era — sprawling and violent, with a dark but clear-eyed view of history.