Games like Super Sunny Island
Games like Super Sunny Island include SANABI, Broforce, Anomaly Agent, Momodora: Reverie Under The Moonlight, and Terminator 2D: NO FATE. We matched them by the tags players give Super Sunny Island on Steam (2D Platformer, Side Scroller, Platformer, Shooter, and Animals): closest matches first, and among equally close ones the better-known games.

SANABI
Shared: 2D Platformer · Platformer · 2D

Broforce
Shared: Platformer · 2D · Side Scroller

Anomaly Agent
Shared: 2D Platformer · Side Scroller · Platformer

Momodora: Reverie Under The Moonlight
Shared: 2D Platformer · Side Scroller · 2D

Terminator 2D: NO FATE
Shared: 2D Platformer · Side Scroller · Shooter

Celeste
Shared: 2D Platformer · Platformer · Pixel Graphics

Webbed
Shared: 2D Platformer · Platformer · Cute

Huntdown
Shared: Side Scroller · Shooter · 2D

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

Nitro Express
Shared: 2D Platformer · Side Scroller · Shooter

Gravity Circuit
Shared: Platformer · 2D Platformer · 2D

Rogue Legacy 2
Shared: Platformer · Arcade · Action

Alex Jones: NWO Wars
Shared: 2D Platformer · Shooter · Side Scroller

Pepper Grinder
Shared: 2D Platformer · Platformer · Arcade

Contra: Operation Galuga
Shared: 2D Platformer · Platformer · Shooter

Mina the Hollower
Shared: 2D Platformer · Action-Adventure · Platformer

Sonic Origins
Shared: 2D Platformer · Platformer · Action

Shovel Knight: Treasure Trove
Shared: Platformer · 2D · Side Scroller

Smilemo
Shared: Platformer · 2D Platformer · Side Scroller

The Elephant Collection
Shared: 2D Platformer · Platformer · Arcade

Skul: The Hero Slayer
Shared: Platformer · 2D · Side Scroller

Sonic Mania
Shared: Platformer · 2D · Side Scroller

Katana ZERO
Shared: Platformer · 2D Platformer · Action

Kero Blaster
Shared: Side Scroller · Platformer · Shooter