Parody in the NFL? Only the players who say "it isn't the money"
on the topic of parity however you've named teams that are on their last legs of being what they typically were.
SF, with the loss of Debartolo isn't the same...the Giants are no force, GB fades with Favre's decline, Den didn't make the playoffs and if you believe that Plummer is going to be another Elway then I'd love to be in your league next year. Oakland is a very good team but their decline is imminent...
Now look at the recent history of the league.. St Louis built quick and faded quick, Tennessee up and down, Carolina and Jax almost gave us an expansion super bowl. Chicago 2 years ago, SD and TB last year, Cleveland...on and on...
What these teams share is that they were together as units and filled in a missing piece or two...that simply isn't the case anymore. Teams are offering shorter contracts which lead to more movement. It's coming down to who can get their chemistry down faster than the rest...the more moving parts you have the more chance for breakdown. The teams you mentioned have less of these parts at the moment...wait a couple of seasons and the field is even for all.