The geometric optics approximation for wave scattering from two-dimensional random rough surfaces is compared to the experimental results from five independent facilities and to the existing numerical electromagnetic theory predictions. The samples include both metallic and dielectric materials with surface slopes ranging from 0.11-0.71. The surface roughness and incident wavelength vary from 0.57-3.58 and from 0.64 microns-3.00 millimeters, respectively. The geometric optics results are in good agreement with all the electromagnetic theory calculations and the experimental findings for the considered two-dimensional surfaces. In addition, the two-dimensional geometric optics approximation predicts both the phenomenon of retro-reflection for surfaces with a slope as low as 0.33 and off-specular peak reflection. For surface parameters within the geometric optics domain of validity for one-dimensional random rough surfaces, the geometric optics results indicate that the one-dimensional domain is valid for two-dimensional surfaces.