Games like Mothership Forever
Games like Mothership Forever include BALL x PIT, Cyberhunt, Voidigo, Halo: Spartan Assault, and Chippy. We matched them by the tags players give Mothership Forever on Steam (Twin Stick Shooter, Shoot 'Em Up, Top-Down Shooter, Simulation, and Roguelike): closest matches first, and among equally close ones the better-known games.

BALL x PIT
Shared: Action · Arcade · Shoot 'Em Up

Cyberhunt
Shared: Shoot 'Em Up · Twin Stick Shooter · Action

Voidigo
Shared: Twin Stick Shooter · Roguelike · Shoot 'Em Up

Halo: Spartan Assault
Shared: Top-Down Shooter · Twin Stick Shooter · Action

Chippy
Shared: Twin Stick Shooter · Shoot 'Em Up · Top-Down Shooter

Nova Drift
Shared: Shoot 'Em Up · Arcade · Roguelike

Police Stories
Shared: Action · Simulation · Top-Down Shooter

Nuclear Throne
Shared: Roguelike · Top-Down Shooter · Action

Relic Hunters Zero: Remix
Shared: Twin Stick Shooter · Top-Down Shooter · Action

Enter the Gungeon
Shared: Roguelike · Twin Stick Shooter · Pixel Graphics

Sky Force Reloaded
Shared: Shoot 'Em Up · Top-Down Shooter · Arcade

SYNTHETIK: Legion Rising
Shared: Top-Down Shooter · Twin Stick Shooter · Action

Sektori
Shared: Twin Stick Shooter · Shoot 'Em Up · Arcade

Beat Hazard
Shared: Twin Stick Shooter · Shoot 'Em Up · Action

Blazing Beaks
Shared: Roguelike · Top-Down Shooter · Action

HELLDIVERS™ Dive Harder Edition
Shared: Twin Stick Shooter · Top-Down Shooter · Action

Turnip Boy Robs a Bank
Shared: Shoot 'Em Up · Top-Down Shooter · Twin Stick Shooter

Waves
Shared: Shoot 'Em Up · Twin Stick Shooter · Arcade

Nex Machina
Shared: Twin Stick Shooter · Shoot 'Em Up · Arcade

Bit Blaster XL
Shared: Shoot 'Em Up · Arcade · Shooter

DoDonPachi Resurrection
Shared: Shoot 'Em Up · Top-Down Shooter · Arcade

The Hong Kong Massacre
Shared: Top-Down Shooter · Twin Stick Shooter · Action

State of Anarchy: Master of Mayhem
Shared: Top-Down Shooter · Twin Stick Shooter · Shoot 'Em Up

LUFTRAUSERS
Shared: Arcade · Shoot 'Em Up · Action