It is hard to say. We Americans regard Yorktown, the Battle of New Orleans, Appomattox, as decisive in retrospect because both the victor and the defeated agreed to some degree.
Lepanto was seen at the time as a great victory by Catholics and other Christians. It was not the end of expansionist Islam but it was certainly the end of their great string of victories.
If the American colonies had not won at Yorktown, they would have continued fighting and eventually the British would have given up because they were too busy fighting elsewhere.
The Battle of New Orleans was meaningless as the war had already ended with the Treaty of Ghent.
The North was winning the Civil War. Appomattox was the last battle, but if the South had won the North would have likely won soon after.