The current playoff format was adopted in 1990. So since then (not counting 2016, obviously), here's the seeding (regardless of conference affiliation) of the eventual Super Bowl winner (26 seasons):
1 seed: 11 (42.3%)
2 seed: 7 (26.9%)
3 seed: 1 (3.8%)
4 seed: 4 (15.4%)
5 seed: 1 (3.8%)
6 seed: 2 (7.7%)
So the #1 seed clearly has the advantage over every other seed, for reasons many people here have cited. Getting a bye in the first round has led to 18 of 26 eventual SB winners (69.2%).
That's pretty remarkable, but understandable. You *can* win it as a lower-four seed (8 out of 26, or 30.8%, which is close enough to 1/3 for our purposes), but it's a huge advantage, obviously, to get a bye and even to have that top seed.