I don't agree that Manning had a garbage OL at all, so we agree there. Indy decided to put more money, more picks, more resources on offense over the years to maximize Peyton's ability, and it worked.
NE, who IMO is perhaps the best run franchise, best coached team in professional sports over the last 13 or so years, put more $ and resources into their defense and OL than they did WR. They honestly lucked into a HOF QB in 6th rd pick Brady and never asked him to be to NE what Peyton was to INDY.
The 3 SuperBowls NE won with Brady were predicated on defense, a tough hard nosed running game with a top OL and with Faulk, Dillon and whatever RB they had.... and some clutch play from Brady. It was also predicated on being a great cold weather power team beating a finesse team built for and used to playing on a fast track in a dome stadium.....and it showed when all those playoff games were played in Foxboro, much more so than when Indy had home field advantage.
NE also had some damn good fortune. If not for the ridiculous tuck rule call when Brady clearly fumbled the ball after being sacked, Oakland goes on to the SuperBowl and NE doesn't win that first one.... and who knows what happens after that.
Bingo. Even at that, the Patriots were not dominant in any of their Super Bowl victories; the margin of victory in each of them was exactly three points. You don't need a great quarterback to win a Super Bowl; sometimes a good QB isn't even a necessity. What you do need is a strong defense. I haven't done an exhaustive analysis, but the following Super Bowl winners, regardless of quarterback play or surrounding offensive personnel, finished in at least the top quartile (and usually, much better) in scoring defense:
1966 Green Bay 1st (163 pts., 14-game regular season until 1978)
1967 Green Bay 3rd (209 pts.)
1969 Kansas City 1st (in AFL with 177 pts.; would have been 2nd if NFL and AFL had been merged that year)
1972 Miami 1st (171 pts.)
1973 Miami 1st (150 pts.)
1974 Pittsburgh 2nd (189 pts.)
1975 Pittsburgh 2nd (162 pts.)
1978 Pittsburgh 1st (195 pts.)
1979 Pittsburgh 7th (262 pts.)
1981 San Francisco 2nd (250 pts.)
1982 Washington 1st (128 pts. in a strike-shortened, nine-game season)
1984 San Francisco 1st (227 pts.)
1985 Chicago 1st (198 pts.)
1986 New York Giants 2nd (236 pts.)
1987 Washington 6th (285 points)
1988 San Francisco 8th (294 pts.)
1989 San Francisco 3rd (253 pts.)
1990 New York Giants 1st (211 pts.)
1991 Washington 2nd (224 pts.)
1992 Dallas 5th (243 pts.)
1993 Dallas 2nd (229 pts.)
1994 San Francisco 6th (296 points)
1995 Dallas 3rd (291 pts.)
1996 Green Bay 1st (210 pts.)
1999 St. Louis 4th (242 pts.)
2000 Baltimore Ravens 1st (165 pts.)
2001 New England 6th (272 pts.)
2002 Tampa Bay 1st (196 pts.)
2003 New England 1st (238 pts.)
2004 New England 2nd (260 pts.)
2005 Pittsburgh 4th (258 pts.)
2008 Pittsburgh 1st (223 pts.)
2010 Green Bay 2nd (240 pts.)
There probably are additional examples which support this predictive model. However, 33 Super Bowl-winning teams, ones with highly variable levels of quarterback play, would strongly urge me, if I was an NFL owner or General Manager, to devote my resources, first and foremost, to building a rock-ribbed defense. If you are going to use a single predictor for success in the Super Bowl, mine would be scoring defense.