Games like Ninja
Games like Ninja include SANABI, Rogue Legacy 2, Celeste, Downwell, and Super Mombo Quest. We matched them by the tags players give Ninja on Steam (Adventure, Action, Arcade, Platformer, and Action-Adventure): closest matches first, and among equally close ones the better-known games.

SANABI
Shared: Action · Adventure · 2D Platformer

Rogue Legacy 2
Shared: Arcade · Action · Platformer

Celeste
Shared: Precision Platformer · Platformer · 2D Platformer

Downwell
Shared: Precision Platformer · Platformer · Arcade

Super Mombo Quest
Shared: Adventure · Action · Arcade

I wanna be the Creator
Shared: Action · Adventure · Platformer

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

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

Shovel Knight: Treasure Trove
Shared: Platformer · Adventure · Action

Sonic Superstars
Shared: Action · Adventure · Platformer

Mark of the Ninja
Shared: Platformer · Action · Adventure

BlazBlue Entropy Effect
Shared: Action · Platformer · Action-Adventure

Jump King
Shared: Adventure · Precision Platformer · Platformer

Trine 5: A Clockwork Conspiracy
Shared: Adventure · Action · Platformer

F.I.S.T.: Forged In Shadow Torch
Shared: Action · Platformer · Adventure

The Messenger
Shared: Platformer · Action · 2D

Hollow Knight
Shared: Platformer · Adventure · 2D

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

Sonic Origins
Shared: Action · Adventure · 2D Platformer

Exit the Gungeon
Shared: Arcade · Action · Adventure

BEEP
Shared: Adventure · Platformer · Action

Volgarr the Viking
Shared: Action · Platformer · Adventure

Skul: The Hero Slayer
Shared: Action · Platformer · Indie

Katana ZERO
Shared: Action · Platformer · 2D Platformer