Ratings of noticed importance individual factors for information system successfulness vary from person to person because everyone has a different level of measurable standards and level of personal importance. The process of ranking is a way to eliminate such individual differences. It generates order which presents relative levels of importance. Information system management should use only the order by importance of successfulness factors of information system to identify relative meaning of one factor among others. It is shown that the order of importance gathered from users is different from the one gathered from information technologies specialists. Such differences emphasize that undertaken process for information system evaluation, partially differentiates between information technology specialists (especially information system managers) and users. Information system management should periodically conduct a survey of the importance of information system successfulness factors noticed by information technologies specialists and users, in order to overcome the differences in importance order between these two groups.