Games like Slime Playgrounds
Games like Slime Playgrounds include Braid, LIMBO, PICO PARK, Trine 2: Complete Story, and Webbed. We matched them by the tags players give Slime Playgrounds on Steam (Early Access, Puzzle Platformer, Side Scroller, 2D Platformer, and Casual): closest matches first, and among equally close ones the better-known games.

Braid
Shared: Puzzle Platformer · 2D Platformer · Puzzle

LIMBO
Shared: Puzzle Platformer · Puzzle · Platformer

PICO PARK
Shared: Puzzle Platformer · Casual · Platformer

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

Webbed
Shared: 2D Platformer · Puzzle Platformer · Cute

The Pedestrian
Shared: Puzzle Platformer · Side Scroller · Puzzle

Öoo
Shared: Puzzle Platformer · 2D Platformer · Puzzle

Planet of Lana
Shared: Puzzle Platformer · 2D Platformer · Puzzle

Pikuniku
Shared: Casual · Puzzle · Cute

Thomas Was Alone
Shared: Side Scroller · 2D Platformer · Puzzle Platformer

BattleBlock Theater®
Shared: Platformer · Funny · 2D

Hue
Shared: Puzzle Platformer · Puzzle · Platformer

Defy Gravity Extended
Shared: Puzzle Platformer · Platformer · Puzzle

Laughing to Die
Shared: Casual · 2D Platformer · Puzzle

CATO: Buttered Cat
Shared: Puzzle Platformer · Puzzle · Cute

KarmaZoo
Shared: Casual · Puzzle Platformer · 2D Platformer

Toki Tori
Shared: Puzzle · Casual · Platformer

Thank Goodness You're Here!
Shared: Casual · 2D Platformer · Funny

Portal 2
Shared: Puzzle · Puzzle Platformer · Platformer

Squishy the Suicidal Pig
Shared: Puzzle Platformer · Puzzle · Platformer

FEZ
Shared: Puzzle · Platformer · Puzzle Platformer

MECCHA CHAMELEON
Shared: Casual · Party Game · Funny

Mind Over Magnet
Shared: Puzzle Platformer · Puzzle · 2D Platformer

Degrees of Separation
Shared: Puzzle Platformer · 2D Platformer · Side Scroller