Games like Sump
Games like Sump include The Beginner's Guide, Little Nightmares, Poppy Playtime, Among the Sleep - Enhanced Edition, and LIMBO. We matched them by the tags players give Sump on Steam (Walking Simulator, Horror, Short, Puzzle, and Experimental): closest matches first, and among equally close ones the better-known games.

The Beginner's Guide
Shared: Walking Simulator · Short · Atmospheric

Little Nightmares
Shared: Horror · Atmospheric · Puzzle

Poppy Playtime
Shared: Horror · Puzzle · Dark

Among the Sleep - Enhanced Edition
Shared: Horror · Walking Simulator · Atmospheric

LIMBO
Shared: Puzzle · Atmospheric · Horror

Layers of Fear (2016)
Shared: Horror · Walking Simulator · Atmospheric

Firewatch
Shared: Walking Simulator · Atmospheric · Adventure

Little Nightmares II
Shared: Horror · Puzzle · Adventure

SOMA
Shared: Horror · Atmospheric · Dark

Outlast
Shared: Horror · Atmospheric · Survival Horror

Paratopic
Shared: Horror · Short · Atmospheric

What Remains of Edith Finch
Shared: Walking Simulator · Atmospheric · Adventure

Amnesia: The Dark Descent
Shared: Horror · Puzzle · Atmospheric

The Room
Shared: Puzzle · Atmospheric · Short

Amnesia: A Machine For Pigs
Shared: Walking Simulator · Horror · Atmospheric

The Room Two
Shared: Puzzle · Horror · Atmospheric

Scorn
Shared: Horror · Puzzle · Atmospheric

Bendy and the Ink Machine
Shared: Horror · Puzzle · Dark

Mouthwashing
Shared: Horror · Walking Simulator · Atmospheric

Inside the Backrooms
Shared: Horror · Puzzle · Adventure

Garten of Banban
Shared: Horror · Puzzle · Walking Simulator

Slender: The Arrival
Shared: Horror · Walking Simulator · Dark

NaissanceE
Shared: Walking Simulator · Atmospheric · Puzzle

Brothers - A Tale of Two Sons
Shared: Atmospheric · Adventure · Puzzle