To assess the sensitivity of microelectronic devices to displacement damage, molecular dynamics simulations of collision cascades in GaN, Si and Ge are performed. We compare results on these three materials using a wide range of data coming from a very large amount of simulations. The statistical analysis of these data probes into the dynamics of cascades in terms of generating defects, the healing process, and the formation of defect clusters. In GaN, we observe that up to 90% of the defects created during a collision cascade initiated by a Ga atom disappear after a few tens of ps. In addition, the larger clusters tend to decrease rapidly in size. At the end, only small clusters remain in GaN, contrary to Si and Ge where large amorphous pockets are present. This metal-like in-cascade defect annealing seems to be closely related to the dense atomic structure of wurtzite GaN. Results confirm that GaN is intrinsically more resistant to non-ionizing radiation than Si and Ge at the studied energies, and over the considered timescales.