What is System Shock 2 and Prey? An FPS? An RPG?
Immersive Sim. This slots in with things like Deus Ex and Dishonored.
Though, now that I think about it, I'm not entirely sure what makes something an im-sim vs just being a first person RPG like say TES:Oblivion. In the context of Prey and System Shock, they have a persistent world where killed enemies (mostly) stay dead and items stay picked up. I don't know if this is the case for games like Deus Ex or Dishonored though, it kind of is true because you play levels, but I think the almost metroidvania feel of Prey and System Shock were a key part of what I now define as an im-sim. But Deus Ex and Dishonored are names that are always trotted out as examples of good im-sims.
Is Selaco an im-sim? I think it is, it has a persistent world which you navigate in a metroidvania style and dead enemies stay dead and picked up items stay picked up. There are upgrades and power ups and light RPG mechanics. However its Steam store page does not list it as one.
So I guess my point is that I know System Shock and Prey are considered Immersive sims but I don't have much of a fucking clue on what that actually means in detail.