Quarterbacks are really important in football. If I was in charge of a team I would want a good one, but I think a great head coach is more valuable than a great quarterback.
A great head coach can manage the team and coach good players to do a great job. He can coach average players to be astonishing, by training them and getting them in shape. The coach can create plays that use the players potential and ability.
The head coach can help pick the players he wants during the draft. A great head coach can inform the players about the importance of the offseason so they don't fall behind. He helps the players stay focused on the game and encourages them to cheer for their teammates. The head coach also leads all the other coaches to success.
Those are a few reasons why I think a great head coach is more important than a great quarterback.