Reasoning for Success or Failure of IS systems/Projects

Now a days , businesses are focusing more and more on the development of information systems and defining the right procedures and business rules to cut costs and gain more and more revenues. ERP systems are being developed and adopted all over the world to get insight information of the businesses. Large and medium sized organizations are tempted to adopt these costly solutions from oracle , SAP , Microsoft and other ERP vendors. My Target audience are those companies who can not invest that much money on these ERP systems or dont want to change their procedures according to these proprietry software solution requisites. Here come the ISVs who can deliver and develop the softwares according the specific requirements of each industry and business. Question is , if ther business requirements are well defined and proposed solution is well aligned with the business requirements ? this is the real cause for the success or failure of IT projects in the recent years.