Games like Probotector II: Return of the Evil Forces

If you finished Probotector II: Return of the Evil Forces, the closest matches are Serious Sam: The First Encounter, Alien Rage: Unlimited, Neptunia Shooter, Ghost in the Shell: Stand Alone Complex - First Assault Online and Mech Arena: Robot Showdown. All 6 share its shooter genre and are ranked by how closely their themes and modes overlap.