I've seen this relatively new meme grow legs somewhere around the time Dallas defeated Philadelphia and took sole possession of first place in the division.
2006: Took three teams to the playoffs: PHI division winner, DAL and NYG wild cards.
2007: Took three teams to the playoffs: DAL division winner (and #1 seed), NYG and WAS wild cards. NYG wins Super Bowl.
2008: Took two teams to the playoffs: defending Super Bowl champ NYG division winner (and #1 seed), PHI wild card (and appeared in NFC title game)
2009: Could potentially take two or three teams to the playoffs again (depending on how Green Bay and Atlanta play the rest of the way)
It's possible that people are simply down on the entire NFC as a whole. Because if not, I don't know how you say the NFC North, South, or West are any better overall.
I try really hard to stay away from conspiracy theories, but it seems that outsiders contort and twist themselves in every way possible and look at every possible angle in an effort to pooh-pooh anything the Cowboys accomplish. The NFC East was the strongest division and either the Eagles and Giants were everyone's SB pick until we took the lead. Now the whole division is overrated
Which brings me to a related question. If everyone says you're overrated, then are you still overrated? Who is overrating you?