I'm going to say sure, great players can make their teams better. Much more so in fact. However it takes more than just one person to be able to win games.

Look at Favre. Great in Green Bay, dismal on the Jets, pretty darn good in Minnesota. Differences were the teams/line/wr's were better in Green Bay and Minnesota. If you are getting sacked every third play, you aren't going to be able to carry your team like in other sports.

Also Adrian Peterson (before all the legal issues) was amazing before last year. All of a sudden parts of the offensive line of MN starts imploding and he goes from best in the league to 'just' really good. If it only takes 2 players on a team to bring a player from almost breaking one of the greatest records in football to average, there is something to be said there.

Note I'm a vikings fan, hence my MN examples.

I don't see how even an exceptional quarterback can be effective if the offensive line and other backs don't block consistently well, or if the receivers don't consistently run the right routes, escape their coverage, actually catch the ball, and run well with it after the catch, or if the running backs don't find the holes the line must create, make good cuts, deflect tackles, and never fumble, or if the place kicker and/or punter don't consistently deliver when one of those things goes wrong, or if despite doing all that stuff right the defense never makes a stop.

Without an offensive line? Yeah right.

Poor o-line. Their importance to recognition ratio is probably one of the greatest injustices in the sport.

A huge part of a quarterback's success is their ability to organize their teammates--through leadership and knowledge--for the best chance of success on every play.