The biggest blowout in NFL championship history was none of the five listed but rather when the Bears beat the Redskins 73-0.
http://en.wikipedia.org/wiki/1940_NFL_Championship_Game
The 1940 National Football League Championship Game, was the 8th in NFL history. The game was played at Griffith Stadium in Washington, D.C. on December 8, 1940. The Chicago Bears defeated the Washington Redskins, 73–0, the most one-sided victory in NFL history. The game was broadcast on radio by Mutual Broadcasting System, the first NFL title game broadcast nationwide.