I mean the 90s EA version, not the boardgame-faithful but divisive recent adaptation. Sure, it doesn't play so well today, but I think it's too overlooked in discussions of that great early-90s surge of PC shooters. This was one of all too few which eschewed the Doom model in favour of something altogether more ambitious.
It was a squad shooter for starters, but it also wove in strategy elements, particularly in a pause-time overmap mode. The idea of limited pause - i.e. you could only use so much of it per mission - to provide breathing space during times of crisis remains a great idea, and one I keep trying to work into things I try/fail to make. Slam on the brakes in order to try and deal with a situation - by which I mean a slavering horde of Genestealers - and even if you can get yourself out of trouble, you've squandered precious pause-time that you will almost certainly need later on.
It threaded into a broader sense of fragility, and the ongoing oddity of heavily-armoured Space Marine Terminators being terrifyingly vulnerable and awkward. A Genestealer's claw is a hot knife through butter; conversely, taking a step is slow and cumbersome. Simply turning ninety degrees takes an age, and is laced with dread about what you might see once the move is completed.
These were not supermen: they were just men being kept barely alive by their power-armour. In dispensing with dice rolls and an overhead view, Space Hulk might have played entirely differently than the boardgame, but the atmosphere of fear and fragility was masterful. Can the more overtly actiony Deathwing possibly come close to that all-encompassing sense of menace?
Also: the Genestealer art was so good.