Games like Stories Best Left Untold
Games like Stories Best Left Untold include The Test, Papers, Please, No, I'm not a Human, The Test: Hypothesis Rising, and Firework. We matched them by the tags players give Stories Best Left Untold on Steam (Simulation, Multiple Endings, Horror, Atmospheric, and Singleplayer): closest matches first, and among equally close ones the better-known games.

The Test
Shared: Simulation · Multiple Endings · Singleplayer

Papers, Please
Shared: Simulation · Indie · Multiple Endings

No, I'm not a Human
Shared: Horror · Singleplayer · Multiple Endings

The Test: Hypothesis Rising
Shared: Simulation · Multiple Endings · Horror

Firework
Shared: Horror · Indie · Atmospheric

INSIDE
Shared: Atmospheric · Horror · Singleplayer

Five Nights at Freddy's
Shared: Horror · Singleplayer · Indie

Homicipher
Shared: Horror · Multiple Endings · Atmospheric

Little Nightmares
Shared: Horror · Atmospheric · Singleplayer

Tiny Bunny
Shared: Horror · Visual Novel · Atmospheric

Five Nights at Freddy's: Security Breach
Shared: Horror · Singleplayer · Multiple Endings

The Test: Final Revelation
Shared: Simulation · Multiple Endings · Horror

Lobotomy Corporation | Monster Management Simulation
Shared: Simulation · Horror · Singleplayer

Emily is Away <3
Shared: Simulation · Multiple Endings · Indie

The Horrorscope
Shared: Simulation · Atmospheric · Multiple Endings

KinitoPET
Shared: Horror · Multiple Endings · Indie

The Mortuary Assistant
Shared: Horror · Atmospheric · Simulation

Outlast
Shared: Horror · Atmospheric · Singleplayer

Volcano Princess
Shared: Multiple Endings · Simulation · Visual Novel

Little Nightmares II
Shared: Horror · Singleplayer · Atmospheric

Poppy Playtime
Shared: Horror · Singleplayer · Indie

Beholder
Shared: Atmospheric · Simulation · Singleplayer

MiSide
Shared: Horror · Singleplayer · Atmospheric

Emily is Away Too
Shared: Simulation · Indie · Multiple Endings