Even the great ones can fall short. No one is undefeated. Rodgers has only won a single Super Bowl. Brady has lost two Super Bowls and should've lost a third before the Russell Wilson pass at the goal line. You haven't seen Eli Manning and Joe Flacco throw interceptions? They suck and have three rings between them.
Cousins is in just his third season as a starter in the NFL. In his first season he finished 5th in passer rating, 7th in DYAR, 6th in QBR. His second season - 3rd in DYAR, 6th in QBR, 3rd in total passing yards.
The guy is a stud. We should throw a parade if Cousins ever puts on a Bills jersey.