Well, to dino's point, I think it's fair to say that the second best team in the NFL was the 49ers, but the NFC can only send one team. I don't forsee a time in the next couple of years where the NFC Champion isn't going to win the Superbowl. The Niners are really good. Arizona caught fire the last half of the season. Carolina is going to be great next year. The Saints will always contend as long as Drew Brees is throwing the football. I don't think there's a whole lot of teams in the AFC that can compete with them. But Denver was the best in the AFC, and that offense was historically good, so that's who the 'Hawks played.
One thing I think that played into the "surprise" aspect of the result is simply how little coverage the Seahawks get nationally. They'll cover Sherman 24/7 when he says something dumb, or Harvin when he's broken (they were 11-0 and the national media was still going on about "Can they win without Harvin?"), but the national media analysts don't really spend a lot of time looking at this team. They knew that the defense was good, but I don't think they really took the time to look and see exactly how good they were. The story line was all focused on Peyton Manning and the Denver "storied franchise" DNA going back to John Elway.
A great example of this was Chris Berman on ESPN interviewing Pete Carroll after the game. Berman wanted to make some point about the decision to defer the opening kickoff (opting to kick, rather than receive) to the Broncos, and turn it into one of those mad scientist type decisions that coaches make. But Pete Carroll does that every game, and has for the last four years. He never opens a game with the ball. He'd rather have possession to open the second half. You would think a guy like Berman would know that. He gets paid to talk about football, but it was pretty clear that he hadn't watched a lot of the Seahawks.
Someday we'll win this thing...