Computer simulations of ecosystems are useful for revealing in detail the ecological processes concerned with major bioevents. Unlike empirical approaches, theoretical models allow us to see virtual evolutionary changes in interspecific interactions in a much shorter time as compared with evolutionary experiments. Some recent ecosystem models succeeded in constructing hypothetical ecosystems with high species diversity by introducing low connectance and gradual evolution. Some of these hypothetical ecosystems had similar properties to real ecosystems. Some models incorporated biologically meaningful rules for constructing interspecific interactions, whereas others did not. Both types of model are complementary to each other: which to choose depends on the purpose of the study. Most of the former type of model focused on incorporating biologically realistic processes. They do not aim to mimic the topological features of real ecosystems. It is quite natural that such models did not reproduce ecosystems similar to real ecosystems. Therefore, the reality of such models should be tested not only by using the topology of the ecosystem but also by using parameters which are suitable for the purpose of the models.