Games like Arth Island
Games like Arth Island include Terraria, Core Keeper, No Man's Sky, The Long Dark, and Don't Starve. We matched them by the tags players give Arth Island on Steam (Exploration, Collectathon, Simulation, Sandbox, and Survival): closest matches first, and among equally close ones the better-known games.

Terraria
Shared: Sandbox · Survival · 2D

Core Keeper
Shared: Exploration · Survival · Open World

No Man's Sky
Shared: Exploration · Open World · Survival

The Long Dark
Shared: Exploration · Survival · Open World

Don't Starve
Shared: Survival · Sandbox · Exploration

Space Engineers
Shared: Sandbox · Simulation · Survival

Slime Rancher
Shared: Exploration · Open World · Sandbox

Starbound
Shared: Sandbox · Survival · Exploration

Project Zomboid
Shared: Survival · Sandbox · Open World

Don't Starve Together
Shared: Survival · Open World · Sandbox

Rain World
Shared: Exploration · Survival · 2D

RimWorld
Shared: Survival · Sandbox · Simulation

The Forest
Shared: Survival · Open World · Exploration

Oxygen Not Included
Shared: Survival · Sandbox · Simulation

Keplerth
Shared: Exploration · Sandbox · Survival

Empyrion - Galactic Survival
Shared: Simulation · Exploration · Survival

7 Days to Die
Shared: Survival · Open World · Exploration

SPORE™
Shared: Sandbox · Exploration · Simulation

鬼谷八荒 Tale of Immortal
Shared: Simulation · Sandbox · Exploration

Forager
Shared: Survival · Sandbox · 2D

Kenshi
Shared: Sandbox · Survival · Open World

Spaceflight Simulator
Shared: Sandbox · Simulation · Exploration

Soulash 2
Shared: Sandbox · Exploration · Simulation

Stardew Valley
Shared: Simulation · Sandbox · Pixel Graphics