This topic shouldn't have even come up until monday if the Patriots win tomorrow, because we have no idea if the Patriots will even win, or if they do, HOW they win.
But, for the point of discussion, I'll asume the Patriots win their next 2 and win the Super Bowl...
I'll still say it's the Steelers. Now, I'm biased because I'm a Pittsburgh fan, but I think most people will agree with me. The 2005 Steelers beat the 1, 2, 3 seeds in the AFC and then went on to beat the #1 NFC seed in the Super Bowl, and all of those games were on the road or at a neutral site, so they had no home games. They dominated the #1 and #2 AFC seeds and it was only close against the Colts because of 2 major flukes (Polamalu INT reversal and Bettis fumble). When considering the Steelers run last year, you also have to look at how they won their final 4 regular season games after being 7-5. When they were 7-5, not a single person on Earth thought they had a chance to win the Super Bowl. Even when they entered the playoffs at 11-5, as the #6 seed, there was still basically no one who thought they actually could win the Super Bowl.
This is not to diss the Patriots this season, they've also had a hell of a run. But really at no point this season were they in danger of missing the playoffs, and they're the #3 seed which has been done before I believe in terms of winning the Super Bowl. If they win it all this year, they'll certainly have had one of the best runs in history, but the 2005 Steelers has to be considered the best.