Games like Inertia
Games like Inertia include Vampire Survivors, Planes, Bullets and Vodka, Cyberhunt, Bit Blaster XL, and LUFTRAUSERS. We matched them by the tags players give Inertia on Steam (Retro, Arcade, Space, 2D, and Sci-fi): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: 2D · Bullet Hell · Arcade

Planes, Bullets and Vodka
Shared: Retro · Arcade · Casual

Cyberhunt
Shared: Arcade · 2D · Retro

Bit Blaster XL
Shared: Arcade · Bullet Hell · 2D

LUFTRAUSERS
Shared: Arcade · 2D · Bullet Hell

Orbt XL
Shared: Arcade · 2D · Score Attack

PAC-MAN™ Championship Edition DX+
Shared: Retro · Arcade · Score Attack

UFO 50
Shared: Retro · Arcade · 2D

Megabonk
Shared: Bullet Hell · Arcade · Survival

Among Us
Shared: Space · 2D · Survival

BALL x PIT
Shared: Arcade · Bullet Hell · 2D

Defy Gravity Extended
Shared: Space · 2D · Sci-fi

Razortron 2000
Shared: Retro · Arcade · Casual

Super Bit Blaster XL
Shared: Arcade · 2D · Bullet Hell

ZeroRanger
Shared: Arcade · Retro · Bullet Hell

DoDonPachi Resurrection
Shared: Arcade · 2D · Bullet Hell

Star Saviors
Shared: Space · Arcade · Bullet Hell

Timberman
Shared: 2D · Arcade · Casual

To The Core
Shared: Arcade · 2D · Casual

UBERMOSH
Shared: Arcade · Retro · Pixel Graphics

Boneraiser Minions
Shared: 2D · Bullet Hell · Arcade

Geometry Wars: Retro Evolved
Shared: Arcade · Retro · 2D

Nova Drift
Shared: Arcade · Bullet Hell · 2D

Broken Armor
Shared: Retro · 2D · Arcade