Games like Demon Go!
Games like Demon Go! include Celeste, Super Meat Boy, Pikuniku, SANABI, and Sonic Origins. We matched them by the tags players give Demon Go! on Steam (Action, Adventure, Casual, Platformer, and 2D Platformer): closest matches first, and among equally close ones the better-known games.

Celeste
Shared: Precision Platformer · Platformer · 2D Platformer

Super Meat Boy
Shared: Platformer · Precision Platformer · 2D Platformer

Pikuniku
Shared: Adventure · Casual · Action

SANABI
Shared: Action · Adventure · 2D Platformer

Sonic Origins
Shared: Action · Adventure · 2D Platformer

Cat Quest
Shared: Adventure · Action · Cute

Sonic Superstars
Shared: Action · Adventure · Platformer

Hollow Knight
Shared: Platformer · 2D · Adventure

Planet of Lana
Shared: Action · 2D Platformer · Adventure

Ori and the Will of the Wisps
Shared: Platformer · Action · Adventure

Pizza Tower
Shared: 2D Platformer · Platformer · Action

Downwell
Shared: Precision Platformer · Platformer · Action

BattleBlock Theater®
Shared: Platformer · Funny · 2D

The Purring Quest
Shared: Platformer · Adventure · Cats

Rayman® Legends
Shared: Adventure · Action · Platformer

Dust: An Elysian Tail
Shared: Action · Platformer · Adventure

Gato Roboto
Shared: Action · Adventure · Platformer

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

Kao the Kangaroo: Round 2 (2003 re-release)
Shared: Adventure · Action · Casual

Jump King
Shared: Adventure · Precision Platformer · Action

The End Is Nigh
Shared: Platformer · Precision Platformer · Adventure

Super Fancy Pants Adventure
Shared: Action · Adventure · Platformer

Brawlhalla
Shared: Casual · 2D Platformer · Platformer

BEEP
Shared: Adventure · Platformer · Action