Barcelona has been around for 113 years. They have won or finished runner-up in La Liga 45 times. Obviously, they've had a lot of great goal scorers to win that many games. At just 24 years old, Messi will obliterate absolutely all of them by the time he hangs up his boots for good.
He has already become Barcelona's leading scorer in club history, setting the record in March 2012 at age 24.