With the existence of numerous rehabilitation systems, classification and comparison becomes difficult, especially due to the many factors involved. Moreover, most current reviews are descriptive and do not provide systematic methods for the visual comparison of systems. This review proposes a method for classifying systems and representing them graphically to easily visualize various characteristics of the different systems at the same time. This method could be an introduction for standardizing the evaluation of gait rehabilitation systems. It evaluates four main modules (body weight support, reciprocal stepping mechanism, pelvis mechanism, and environment module) of 27 different gait systems based on a set of characteristics. The combination of these modular evaluations provides a description of the system 'in the space of rehabilitation.' The evaluation of each robotic module, based on specific characteristics, showed diverse tendencies. While there is an augmented interest in developing more sophisticated reciprocal stepping mechanisms, few researchers are dedicated to enhance the properties of pelvis mechanisms.