Games like Splinter Zone
Games like Splinter Zone include Skul: The Hero Slayer, 20XX, 30XX, Dungreed, and Risk of Rain (2013). We matched them by the tags players give Splinter Zone on Steam (Colorful, Action Roguelike, Action, Side Scroller, and Female Protagonist): closest matches first, and among equally close ones the better-known games.
Skul: The Hero Slayer
Shared: Action Roguelike · Action · Roguelite
20XX
Shared: Action Roguelike · Action · Platformer
30XX
Shared: Action Roguelike · Side Scroller · Platformer
Dungreed
Shared: Action Roguelike · Action · Roguelite
Risk of Rain (2013)
Shared: Action Roguelike · Action · Platformer
Rogue Legacy
Shared: Action Roguelike · Platformer · Action
Vampire Survivors
Shared: Action Roguelike · Roguelite · 2D
Celeste
Shared: Difficult · Platformer · Female Protagonist
Geometry Dash
Shared: Difficult · Colorful · Platformer
Anomaly Agent
Shared: Action Roguelike · Side Scroller · Platformer
Hades II
Shared: Action · Action Roguelike · Roguelite
Momodora: Reverie Under The Moonlight
Shared: Side Scroller · Female Protagonist · 2D Platformer
Hades
Shared: Action Roguelike · Action · Roguelite
Dead Cells
Shared: Action Roguelike · Roguelite · 2D
Caveblazers
Shared: Action Roguelike · Platformer · Roguelite
SANABI
Shared: Action · 2D Platformer · Platformer
BlazBlue Entropy Effect
Shared: Action Roguelike · Action · Platformer
Rogue Legacy 2
Shared: Action · Platformer · Roguelite
Sonic Mania
Shared: Platformer · Colorful · 2D
The Binding of Isaac: Rebirth
Shared: Action Roguelike · Difficult · 2D
Spelunky
Shared: Action Roguelike · Platformer · Difficult
Sundered®: Eldritch Edition
Shared: Action Roguelike · Platformer · Female Protagonist
Downwell
Shared: Action Roguelike · Platformer · Action
Super Meat Boy
Shared: Platformer · Difficult · 2D Platformer