Games like Project Delta
Games like Project Delta include Hollow Knight, ANIMAL WELL, Axiom Verge, The Messenger, and Hollow Knight: Silksong. We matched them by the tags players give Project Delta on Steam (Procedural Generation, Metroidvania, 2D Platformer, Retro, and Exploration): closest matches first, and among equally close ones the better-known games.

Hollow Knight
Shared: Metroidvania · Platformer · 2D

ANIMAL WELL
Shared: Metroidvania · Exploration · Platformer

Axiom Verge
Shared: Metroidvania · Platformer · Pixel Graphics

The Messenger
Shared: Metroidvania · Retro · Platformer

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

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

Rain World
Shared: Exploration · Platformer · 2D

Momodora: Reverie Under The Moonlight
Shared: Metroidvania · 2D Platformer · Exploration

SANABI
Shared: 2D Platformer · Pixel Graphics · Action

VVVVVV
Shared: 2D Platformer · Platformer · Retro

Dead Cells
Shared: Metroidvania · 2D · Pixel Graphics

Gato Roboto
Shared: Metroidvania · Action · 2D

F.I.S.T.: Forged In Shadow Torch
Shared: Metroidvania · Platformer · 2D Platformer

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

Haiku, the Robot
Shared: Metroidvania · Exploration · 2D Platformer

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

CARRION
Shared: Metroidvania · Pixel Graphics · Horror

Owlboy
Shared: Metroidvania · Platformer · Pixel Graphics

Blasphemous 2
Shared: Metroidvania · 2D Platformer · Fantasy

Himno
Shared: Procedural Generation · Platformer · 2D

Environmental Station Alpha
Shared: Metroidvania · Platformer · Retro

Bloodstained: Curse of the Moon
Shared: Retro · Metroidvania · Platformer

Castlevania Advance Collection
Shared: Metroidvania · 2D Platformer · Retro

Blasphemous
Shared: Metroidvania · 2D · Pixel Graphics