Games like The Line
Games like The Line include Portal 2, Portal, Chained Together, LIMBO, and Human Fall Flat. We matched them by the tags players give The Line on Steam (Puzzle, Experimental, 3D Platformer, Puzzle Platformer, and Precision Platformer): closest matches first, and among equally close ones the better-known games.

Portal 2
Shared: Puzzle · Platformer · Puzzle Platformer

Portal
Shared: Puzzle · Puzzle Platformer · 3D Platformer

Chained Together
Shared: Platformer · Puzzle Platformer · 3D Platformer

LIMBO
Shared: Puzzle · Puzzle Platformer · Platformer

Human Fall Flat
Shared: Puzzle · Puzzle Platformer · Physics

Climber Animals: Together
Shared: Puzzle Platformer · 3D Platformer · Platformer

The Pedestrian
Shared: Puzzle · Puzzle Platformer · Logic

Viewfinder
Shared: Puzzle · Puzzle Platformer · Physics

Refunct
Shared: 3D Platformer · Puzzle Platformer · Parkour

Tomb Raider IV-VI Remastered
Shared: Puzzle · 3D Platformer · Platformer

Quantum Conundrum
Shared: Puzzle · Puzzle Platformer · 3D Platformer

Moncage
Shared: Puzzle · Experimental · Casual

Trine 3: The Artifacts of Power
Shared: Puzzle Platformer · 3D Platformer · Puzzle

A Story About My Uncle
Shared: Puzzle · 3D Platformer · Parkour

Biped
Shared: Puzzle · Puzzle Platformer · 3D Platformer

Supraland
Shared: Puzzle Platformer · Puzzle · 3D Platformer

EDGE
Shared: Puzzle · Puzzle Platformer · Platformer

Papo & Yo
Shared: 3D Platformer · Puzzle Platformer · Puzzle

Tiny and Big: Grandpas Leftovers
Shared: Puzzle · 3D Platformer · Platformer

FEZ
Shared: Puzzle · Platformer · Puzzle Platformer

Carry The Glass
Shared: Puzzle Platformer · 3D Platformer · Platformer

Trine 2: Complete Story
Shared: Puzzle Platformer · Puzzle · Platformer

Defy Gravity Extended
Shared: Puzzle · Puzzle Platformer · Platformer

SEUM: Speedrunners from Hell
Shared: 3D Platformer · Precision Platformer · Parkour