Haven't we been through this already? Like, every single year? I don't feel like rewriting my original post from 2010, but the facts have only been strengthened since. Jayson Stark has once again articulated this much better than I could.
Anyway you look at it - whether it's Super Bowl Champs vs. World Series winners, or playoff teams, or the spread amongst teams' regular season records, there is very little parity in the the NFL compared to the MLB.
Anyhow, I always look forward to the Super Bowl. Means Spring Training is right around the corner :)