Focus on every customer. Treating happy customers well would motivate them to bring in more customers. If you focus only on the unhappy ones, you might lose the happy ones.
Happy customers will definitely bring more customers whether you take notice of it or not. Focusing on the unhappy ones make you see the shortcoming of your business. It is obvious that everyone is taken care of but troubleshooting the problem behind the unhappy customer will greatly boost the service of your company. Besides, it will only need 1 unhappy customer to lose lots of potential clients.
I do agree with the reply that not everyone is made to be a boss. If everyone is a boss then there will be no people to hire to manage and maintain our business needs. There are people who have a knack for business while others love to compete in a corporate world where they feel proud when they are recognized as a top employee.