Games like Gnarly Hike
Games like Gnarly Hike include Outlast, Phasmophobia, Five Nights at Freddy's, SOMA, and Poppy Playtime. We matched them by the tags players give Gnarly Hike on Steam (First-Person, Psychological Horror, Difficult, Atmospheric, and Action-Adventure): closest matches first, and among equally close ones the better-known games.

Outlast
Shared: First-Person · Psychological Horror · Atmospheric

Phasmophobia
Shared: Psychological Horror · First-Person · Supernatural

Five Nights at Freddy's
Shared: Psychological Horror · Difficult · First-Person

SOMA
Shared: Psychological Horror · Atmospheric · First-Person

Poppy Playtime
Shared: First-Person · Psychological Horror · Singleplayer

Ghostwire: Tokyo
Shared: First-Person · Supernatural · Action-Adventure

What Remains of Edith Finch
Shared: Atmospheric · First-Person · Psychological Horror

MiSide
Shared: Psychological Horror · First-Person · Atmospheric

No, I'm not a Human
Shared: Psychological Horror · Atmospheric · First-Person

Outlast 2
Shared: Psychological Horror · First-Person · Atmospheric

Layers of Fear (2016)
Shared: Psychological Horror · First-Person · Atmospheric

Firewatch
Shared: Atmospheric · First-Person · Adventure

Five Nights at Freddy's 2
Shared: Psychological Horror · First-Person · Difficult

Pacify
Shared: Psychological Horror · First-Person · Supernatural

Little Nightmares II
Shared: Psychological Horror · Atmospheric · Dark

Amnesia: Rebirth
Shared: First-Person · Action-Adventure · Atmospheric

Visage
Shared: Psychological Horror · First-Person · Atmospheric

Mouthwashing
Shared: Psychological Horror · Atmospheric · Horror

Sally Face - Episode One
Shared: Psychological Horror · Dark · Atmospheric

Ultimate Custom Night
Shared: Difficult · First-Person · Singleplayer

Still Wakes the Deep
Shared: Psychological Horror · First-Person · Atmospheric

Five Nights at Freddy's 4
Shared: First-Person · Difficult · Psychological Horror

Ready or Not
Shared: First-Person · Realistic · Psychological Horror

Five Nights at Freddy's: Sister Location
Shared: First-Person · Difficult · Dark