12. Deadwood (2004-2006)
Image Source: IMDb
While the overall plot and storylines (featuring portrayals of real-life time-period figures) for this Old West series was brilliant, the true strength of Deadwood was its massively successful ensemble cast. From Ian McShane to John Hawkes to Keith Carradine to Powers Boothe, the professionalism within the cast is tough to beat in terms of a regular television series.