Games like Sir Fallen
Games like Sir Fallen include Celeste, Jump King, Super Meat Boy, Geometry Dash, and VVVVVV. We matched them by the tags players give Sir Fallen on Steam (Psychological Horror, Precision Platformer, Difficult, 2D Platformer, and Hidden Object): closest matches first, and among equally close ones the better-known games.

Celeste
Shared: Precision Platformer · Difficult · 2D Platformer

Jump King
Shared: Psychological Horror · Precision Platformer · Difficult

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

Geometry Dash
Shared: Difficult · Precision Platformer · 2D

VVVVVV
Shared: Precision Platformer · 2D Platformer · Difficult

SANABI
Shared: 2D Platformer · Action · Pixel Graphics

Hollow Knight
Shared: Difficult · Platformer · 2D

Downwell
Shared: Precision Platformer · 2D Platformer · Platformer

Pogostuck: Rage With Your Friends
Shared: Psychological Horror · Precision Platformer · Difficult

Rain World
Shared: Difficult · Platformer · 2D

I wanna be the Creator
Shared: Difficult · Platformer · Precision Platformer

Changed
Shared: Psychological Horror · Difficult · Cute

Bread & Fred
Shared: 2D Platformer · Difficult · Precision Platformer

Katana ZERO
Shared: 2D Platformer · Platformer · Action

A Difficult Game About Climbing
Shared: Psychological Horror · Difficult · Precision Platformer

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

Ambidextro
Shared: Precision Platformer · 2D Platformer · Platformer

Hollow Knight: Silksong
Shared: Difficult · 2D · Platformer

Getting Over It with Bennett Foddy
Shared: Psychological Horror · Difficult · Platformer

Blasphemous 2
Shared: Difficult · 2D Platformer · Fantasy

Shovel Knight: Treasure Trove
Shared: Platformer · Difficult · 2D

Momodora: Reverie Under The Moonlight
Shared: 2D Platformer · Difficult · 2D

Skul: The Hero Slayer
Shared: 2D · Action · Difficult

Pizza Tower
Shared: 2D Platformer · Platformer · Indie