Games like Celtreos
Games like Celtreos include Jets'n'Guns Gold, LUFTRAUSERS, Cuphead, ZeroRanger, and Star Saviors. We matched them by the tags players give Celtreos on Steam (Shoot 'Em Up, Side Scroller, Bullet Hell, Indie, and Gun Customization): closest matches first, and among equally close ones the better-known games.
Jets'n'Guns Gold
Shared: Shoot 'Em Up · Side Scroller · Great Soundtrack
LUFTRAUSERS
Shared: Bullet Hell · Indie · Shoot 'Em Up
Cuphead
Shared: Great Soundtrack · Indie · Bullet Hell
ZeroRanger
Shared: Shoot 'Em Up · Bullet Hell · Indie
Star Saviors
Shared: Shoot 'Em Up · Bullet Hell · Indie
Ikaruga
Shared: Shoot 'Em Up · Bullet Hell · Great Soundtrack
Jets'n'Guns 2
Shared: Shoot 'Em Up · Indie · Side Scroller
DARIUSBURST Chronicle Saviours
Shared: Shoot 'Em Up · Side Scroller · Great Soundtrack
Streets of Rage 4
Shared: Indie · Action · Side Scroller
Nova Drift
Shared: Shoot 'Em Up · Bullet Hell · Arcade
Guns, Gore & Cannoli
Shared: Side Scroller · Shoot 'Em Up · Action
Bit Blaster XL
Shared: Shoot 'Em Up · Bullet Hell · Arcade
Revolution Ace
Shared: Shoot 'Em Up · Bullet Hell · Indie
Broforce
Shared: Action · Indie · Side Scroller
Savant - Ascent
Shared: Indie · Shoot 'Em Up · Great Soundtrack
METAL SLUG 3
Shared: Side Scroller · Arcade · Action
Jet Lancer
Shared: Indie · Shoot 'Em Up · Action
METAL SLUG
Shared: Side Scroller · Shoot 'Em Up · Action
Sky Force Reloaded
Shared: Shoot 'Em Up · Bullet Hell · Arcade
Touhou Tenkuushou ~ Hidden Star in Four Seasons.
Shared: Bullet Hell · Shoot 'Em Up · Great Soundtrack
Huntdown
Shared: Side Scroller · Shoot 'Em Up · Action
Just Shapes & Beats
Shared: Bullet Hell · Great Soundtrack · Indie
Touhou Koumakyou: New Classic - the Embodiment of Scarlet Devil
Shared: Shoot 'Em Up · Bullet Hell · Great Soundtrack
Beat Hazard
Shared: Shoot 'Em Up · Bullet Hell · Indie