NFL's greatest dynasties of the past six decades: Patriots, Steelers battle for top spot

In a world of unknowns, there are several assurances that are as consistent as the four seasons. If you're a sports fan, you know that every year, a new champion in each league is crowned. The NFL, for example, has crowned a champion every year since its inception in 1920. Some teams have enjoyed more championship success than others, while some fan bases are still waiting for their day in the sun.