Games like Radirgy Swag
Games like Radirgy Swag include Touhou Koumakyou: New Classic - the Embodiment of Scarlet Devil, Planes, Bullets and Vodka, Bit Blaster XL, LUFTRAUSERS, and Vampire Survivors. We matched them by the tags players give Radirgy Swag on Steam (Bullet Hell, Action, Shoot 'Em Up, Singleplayer, and 2D): closest matches first, and among equally close ones the better-known games.

Touhou Koumakyou: New Classic - the Embodiment of Scarlet Devil
Shared: Bullet Hell · Shoot 'Em Up · Action

Planes, Bullets and Vodka
Shared: Action · Shoot 'Em Up · Bullet Hell

Bit Blaster XL
Shared: Bullet Hell · Shoot 'Em Up · Shooter

LUFTRAUSERS
Shared: Bullet Hell · Action · Shoot 'Em Up

Vampire Survivors
Shared: Bullet Hell · 2D · Singleplayer

Touhou Kouryudou ~ Unconnected Marketeers.
Shared: Bullet Hell · Action · Shoot 'Em Up

BALL x PIT
Shared: Action · Bullet Hell · Shoot 'Em Up

DRAINUS
Shared: Action · Shoot 'Em Up · Singleplayer

Touhou Juuouen 〜 Unfinished Dream of All Living Ghost.
Shared: Action · Bullet Hell · Shoot 'Em Up

Nova Drift
Shared: Bullet Hell · Shoot 'Em Up · Shooter

Star Saviors
Shared: Bullet Hell · Shoot 'Em Up · Action

Revolution Ace
Shared: Action · Shoot 'Em Up · Bullet Hell

Ikaruga
Shared: Bullet Hell · Shoot 'Em Up · Action

Touhou Kinjoukyou ~ Fossilized Wonders.
Shared: Bullet Hell · Shoot 'Em Up · Action

Mushihimesama
Shared: Bullet Hell · Shoot 'Em Up · Action

ZeroRanger
Shared: Bullet Hell · Shoot 'Em Up · Action

Star of Providence
Shared: Bullet Hell · Shoot 'Em Up · Action

Call of Duty®
Shared: Action · Singleplayer · Shooter

Zombotron
Shared: Action · 2D · Singleplayer

BioShock Infinite
Shared: Action · Shooter · Singleplayer

Grand Theft Auto V Legacy
Shared: Action · Shooter · Singleplayer

Touhou Kaeizuka ~ Phantasmagoria of Flower View.
Shared: Action · Shoot 'Em Up · Bullet Hell

Touhou Fuujinroku ~ Mountain of Faith.
Shared: Action · Bullet Hell · Shoot 'Em Up

Beat Hazard
Shared: Bullet Hell · Shoot 'Em Up · 2D