I would rank the Top 5 teams in this game like this...
1-San Diego
2-Philadelphia
3-Indianapolis
4-Dallas
5-New Orleans
The two most underrated teams are Carolina and San Fran.
Carolina has everything the top teams I mentioned have, except their QB sucks. Infact, other than at QB...I'd argue that they're better than some of the widely accepted best teams in Madden. If they had a QB like Rivers, the Panthers are a Top 3 team in the game.
San Fran is a very unique team. Gore is awesome, and Coffee is very underrated. Davis is one of the Top 5 most dangerous offensive weapons in Madden in my opinion, and probably the toughest non-running back to stop.
Defensively, is there a faster pair of linebackers than Willis and Lawson?
I think you can play more base defense against spread sets and get away with it with San Fran, than you can with any other defense in the game. That's why they're underrated.