Games like The Attic
Games like The Attic include Firework, Layers of Fear (2016), OMORI, Mouthwashing, and THE LONGING. We matched them by the tags players give The Attic on Steam (RPG, Walking Simulator, Choose Your Own Adventure, 2D, and Comic Book): closest matches first, and among equally close ones the better-known games.

Firework
Shared: 2D · Horror · Psychological Horror

Layers of Fear (2016)
Shared: Walking Simulator · First-Person · Horror

OMORI
Shared: RPG · Psychological Horror · 2D

Mouthwashing
Shared: Walking Simulator · Horror · Psychological Horror

THE LONGING
Shared: Walking Simulator · Choose Your Own Adventure · 2D

Slay the Princess — The Pristine Cut
Shared: Choose Your Own Adventure · Psychological Horror · Horror

KARMA: The Dark World
Shared: Walking Simulator · First-Person · Horror

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

What Remains of Edith Finch
Shared: Walking Simulator · First-Person · Mystery

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

Still Wakes the Deep
Shared: Walking Simulator · First-Person · Horror

Outlast
Shared: First-Person · Horror · Psychological Horror

The Test
Shared: Choose Your Own Adventure · Psychological Horror · Psychological

Garten of Banban
Shared: First-Person · Horror · Psychological Horror

Dagon: by H. P. Lovecraft
Shared: First-Person · Horror · Choose Your Own Adventure

Mundaun
Shared: Walking Simulator · Hand-drawn · Horror

Ib
Shared: 2D · RPG · Horror

Blair Witch
Shared: First-Person · Horror · Walking Simulator

The Cabin Factory
Shared: Walking Simulator · Horror · First-Person

Slender: The Arrival
Shared: First-Person · Horror · Walking Simulator

From The Darkness
Shared: Walking Simulator · First-Person · Horror

Milk outside a bag of milk outside a bag of milk
Shared: Psychedelic · Psychological Horror · 2D

While We Wait Here
Shared: Choose Your Own Adventure · Walking Simulator · Horror

Firewatch
Shared: Walking Simulator · First-Person · Mystery