Some great suggestions on here: Elite, Turbo Esprit, Sabre Wolf brings back some good memories of my Spectrum 48 days, I had many an hour wasted plaing Commando & Green Beret (again probably not underrated).
My favorite from back then was Quazatron:
Actually downloaded it with an emulation pack a couple of years back, unfortunately the fustration caused playing it, didn’t translate well 😳
Slightly more up to date (but not too much) & maybe more I remember as their game play was great (maybe another thread in the making?):
Systemshock, you can have monster jump out at you left and right in Doom et all, but the downright spooky calls of the Ai in the this game were great atmosphere-wise (Bio-shock was a contempory apparently) & the lack of ammo meant you couldn’t just run amok with your gun. Though Wiki kinda suggest it did “moderately successful”, so may not really come under the “underrated title”
Also there was an IGN modern day soldier/assasin RPG game I can’t recall the name of (damn thats fustrating, and IGN have release quite a few games)
oh and Max Payne’s bullet time, cool as ****