Prior to 1945, the three most important teams were:
Packers
Bears. The 1940s Bears are a dynasty comparable to the 50s Browns, 60s Packers, and 70s Steelers. Feel free to ask Dan Daly on Twitter about these Bears.
Commanders (those Sammy Baugh teams were good)
imo all iconic. But probably recognizable only to history buffs.
1945-1950
no teams I'd regard as iconic, but historically important were the Cleveland/LA Rams and the Eagles. the Rams have the best O in the history of the NFL.
the Eagles Steve Van Buren was the best RB prior to Jim Brown, and the defense Greasy Neale created was what everyone was playing before the 4-3.
1950-1955
Two teams counted. the Browns and the Detroit Lions. iconic.
1956-1961
NY Giants and the Baltimore Colts. iconic.
1962-1967
Green Bay Packers. This version is iconic.
1971-1980
Steelers, Cowboys, Dolphins, Raiders. IMO, all 4 are iconic.
1981-1991
49ers, Commanders, NY Giants. All 3 iconic.
1992-1995
Dallas Cowboys.
1996 to present
Denver Broncos - Elway teams. iconic to me
St Louis Rams - Warner teams. iconic.
New England Patriots - yes, iconic.
Pittsburgh. tend to think the second best team of this period.
Seattle. Also a very good and historic team. Not sure if they are iconic.
NY Giants. important in this period and I'm sure their fans love them.
And yes, it's broken down by time periods as most folks notion of iconic is at best 1962 onwards.
D-