Many of the games here are not in any way underrated. Old, and maybe forgotten... But underrated? Nope.
Prey. No One Lives Forever. Battlefield 2142. All from page one. All absolutely massive when they were released.
agree, most are just old and fondly remembered instead of underrated.
Would love to say Planetside, as I truly feel the original was well ahead of its time and massively underrated/overlooked, but I know it was still pretty popular (in its peak) and spawned a sequel, so hardly some under the radar gem...
Giants Citizen Kabuto was another that came to mind, and it's good it's been mentioned. but again, it was pretty well advertised at the time, but admittedly the sales weren't as good as the game deserved.
Sacrifice - again, epic. But, I can remember it being advertised and regarded highly at the time.
Interstate 76??? That was amazing too - but it spawned a sequel so wasn't a hidden gem either.
Battlezone from the mid 90s? again, probably pretty well know in its time.