Games like Requiem
Games like Requiem include The Room 4: Old Sins, The Room, Poppy Playtime, The House of Da Vinci, and Riven. We matched them by the tags players give Requiem on Steam (Adventure, Hidden Object, Casual, Puzzle, and 3D): closest matches first, and among equally close ones the better-known games.

The Room 4: Old Sins
Shared: Adventure · Puzzle · Hidden Object

The Room
Shared: Puzzle · Adventure · Hidden Object

Poppy Playtime
Shared: Puzzle · Singleplayer · Adventure

The House of Da Vinci
Shared: Hidden Object · Puzzle · Adventure

Riven
Shared: Adventure · Puzzle · Singleplayer

The Room Two
Shared: Puzzle · Hidden Object · Adventure

Monument Valley
Shared: Adventure · Puzzle · Casual

The Room Three
Shared: Adventure · Puzzle · Hidden Object

Boxes: Lost Fragments
Shared: Adventure · Puzzle · Casual

Outer Wilds
Shared: Adventure · Exploration · Puzzle

Moncage
Shared: Casual · Puzzle · Adventure

Firewatch
Shared: Adventure · Singleplayer · First-Person

Five Nights at Freddy's: Security Breach
Shared: Singleplayer · Adventure · 3D

Blue Prince
Shared: Puzzle · Adventure · Exploration

Portal 2
Shared: Puzzle · Singleplayer · First-Person

Slime Rancher
Shared: Adventure · Singleplayer · Exploration

Quern - Undying Thoughts
Shared: Adventure · Puzzle · Singleplayer

Indiana Jones and the Great Circle
Shared: Adventure · Puzzle · Singleplayer

Spirit of the North
Shared: Adventure · Puzzle · Casual

Superliminal
Shared: Puzzle · Thriller · Singleplayer

The Witness
Shared: Puzzle · Exploration · Singleplayer

Platform 8
Shared: Adventure · Hidden Object · Puzzle

Sherlock Holmes: The Devil's Daughter
Shared: Adventure · Puzzle · Thriller

Myst
Shared: Adventure · Puzzle · Exploration