Enterprise System (ES) providers may create an ecosystem around their solution permitting other software companies to develop and distribute software that enhances, extends or modifies enterprise systems. This contribution takes a closer look at the business model of companies that are part of an ecosystem through various comparative case studies. Companies have been evaluated according to their business model and success in two steps: a standardized survey and in-depth interviews. Based on the results a model was derived that visualizes the fact that companies success is related to their consulting intensity, volume of sold licenses and degree of standardization of the software they provide. From this fact a classification model has been created and introduced, which can also be applied to evaluating business models and success of companies that are not members of an ES ecosystem.