And since 1993.. a stretch of 20 years, the #1 and #1 in each conference have only met in the SuperBowl twice. Once in '93 when the Cowboys beat the Bills, and once last season when the Seahawks beat the Broncos. That my friends is a 10% ratio of the "best usually going to the Superbowl".
http://www.pro-football-reference.com/blog/?p=5696
Which means, 90% of the time, the Superbowl is played by two teams who are not necessarily the best in the regular season (that number is very skewed, because often it is one of the #1 seeds, but not the other), and the winner of the SuperBowl has been a team ranked other than a #1 seed.
In fact, since 1993, that same 20 year stretch, only the Cowboys, Saints, and Seahawks have won the Superbowl while being the top seed in the NFC, and the '98 Broncos and '03 Patriots are the only AFC teams to do it.
Five teams in 20 years have won while being the #1 seed in their conference, and two of those years, no matter which team won the SuperBowl, it would have been the #1 seed.
That means only 25% of the time does a #1 seed actually win the big game. 75% of the time, a team other than the #1 seed wins it.
That is a huge ratio difference, and should serve to dispel the myth that "usually" the best teams win, or even make it, to the SuperBowl.
10% of the time, over a 20 year stretch, have the two best teams played one another, and 75% of the time the SuperBowl is won by a team other than one of the best two teams, just to sum all that up.