In this study, we develop a methodology to evaluate and benchmark the European Ground Motion Service (EGMS) products. Our approach integrates Global Navigation Satellite Systems (GNSS) measurements and measurements at and around corner reflectors (CRs), targeting the three product levels of the EGMS. We employ statistical tests to identify significant differences in the comparisons, focusing on time series, velocity estimation, and geopositioning. The study applies this practical methodology to evaluate the first EGMS product from 2015 and 2021 over various European test sites with significant surface deformation. The results consistently demonstrate a solid time series and velocity correlation between EGMS and GNSS at the tested sites, with, e.g., most of the differences between velocities being below 2 mm/year. This methodology, implemented in Python notebooks, ensures reproducible results and allows for validating the EGMS over other locations.