I did multiple playthroughs, over ~150h. I do not expect to return to it, now that EDF6 is out. It reaaaaaally resembles EDF5. From what I have seen thus far, it could be called an “expandalone”. There is much more difference between EDF4.1 and EDF5 than EDF5 and EDF6
A bit of an acquired taste, but the entire Earth Defence Force series can be played split screen (2P only). The best entry point into the series is EDF 5 (story reboot, QoL tweaks) which is often deeply discounted. Plus its direct sequel EDF 6 just released in the west last month