Games like The Down Below
Games like The Down Below include Half-Life 2, METRO Last Light Redux, BioShock Infinite, Black Mesa, and METRO 2033 Redux. We matched them by the tags players give The Down Below on Steam (Action, Adventure, Shooter, FPS, and Immersive Sim): closest matches first, and among equally close ones the better-known games.

Half-Life 2
Shared: Action · FPS · Shooter

METRO Last Light Redux
Shared: Action · FPS · Atmospheric

BioShock Infinite
Shared: Action · Shooter · FPS

Black Mesa
Shared: Action · FPS · Shooter

METRO 2033 Redux
Shared: FPS · Action · Atmospheric

Metro Exodus
Shared: FPS · Action · Atmospheric

Counter-Strike 2
Shared: Shooter · FPS · Action

Aimlabs
Shared: FPS · Shooter · Action

Fallout 4
Shared: Adventure · Shooter · Action

Atomic Heart
Shared: Adventure · Action · FPS

System Shock
Shared: Action · Adventure · Immersive Sim

DOOM
Shared: Action · FPS · Shooter

BioShock™ Remastered
Shared: FPS · Action · Atmospheric

S.T.A.L.K.E.R.: Shadow of Chornobyl - Enhanced Edition
Shared: Action · Adventure · Shooter

Half-Life: Alyx
Shared: FPS · Shooter · Action

BioShock™
Shared: Action · FPS · Atmospheric

Apex Legends™
Shared: FPS · Shooter · Action

Ready or Not
Shared: Shooter · FPS · Action

Far Cry 3
Shared: Action · Adventure · FPS

Left 4 Dead 2
Shared: FPS · Shooter · Action

S.T.A.L.K.E.R. 2: Heart of Chornobyl - Standard Edition
Shared: FPS · Shooter · Atmospheric

DOOM Eternal
Shared: Action · FPS · Shooter

PUBG: BATTLEGROUNDS
Shared: Shooter · FPS · Action

Call of Duty®: Black Ops III
Shared: Action · Shooter · FPS