Games like Still Rain: The Arrival
Games like Still Rain: The Arrival include Firewatch, What Remains of Edith Finch, Layers of Fear (2016), MiSide, and Amnesia: A Machine For Pigs. We matched them by the tags players give Still Rain: The Arrival on Steam (Psychological Horror, Adventure, Horror, First-Person, and Atmospheric): closest matches first, and among equally close ones the better-known games.

Firewatch
Shared: Adventure · Atmospheric · Story Rich

What Remains of Edith Finch
Shared: Atmospheric · Story Rich · First-Person

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

MiSide
Shared: Psychological Horror · Horror · Story Rich

Amnesia: A Machine For Pigs
Shared: Horror · Psychological Horror · First-Person

SOMA
Shared: Psychological Horror · Horror · Atmospheric

Outer Wilds
Shared: Adventure · Exploration · Story Rich

Mouthwashing
Shared: Psychological Horror · Horror · Atmospheric

Fears to Fathom - Ironbark Lookout
Shared: Psychological Horror · Horror · Atmospheric

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

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

Sally Face - Episode One
Shared: Psychological Horror · Horror · Story Rich

Lethal Company
Shared: Horror · First-Person · Psychological Horror

Outlast
Shared: Horror · First-Person · Psychological Horror

The Park®
Shared: Psychological Horror · Horror · First-Person

Little Nightmares II
Shared: Adventure · Horror · Psychological Horror

No, I'm not a Human
Shared: Psychological Horror · Horror · Story Rich

Psalm 5:9-13
Shared: Psychological Horror · Horror · Exploration

Subliminal
Shared: Psychological Horror · Atmospheric · Horror

Escape the Backrooms
Shared: Horror · Psychological Horror · First-Person

The Beast Inside
Shared: Adventure · Horror · First-Person

Blair Witch
Shared: Adventure · Psychological Horror · Horror

INFRA
Shared: First-Person · Atmospheric · Adventure

Visage
Shared: Psychological Horror · Horror · First-Person