That sounded a little off, so I looked it up ... they were great last year, but the year before, in 2010 they ranked 16th in Opponents PPG with 21.6, and 13th in total yards against.
I agree that the 49ers should have beat NY, but to say they should have won the superbowl is a bit of a stretch ? I mean, they lost to NY in the same fashion that they beat the Saints, with crazy turnovers. So while they may have been unlucky in losing to NY, they were lucky to beat the saints.