Games like Moonbase Down
Games like Moonbase Down include UFO 50, Notes of Soul, Vampire Survivors, Mount & Blade II: Bannerlord, and Darkwood. We matched them by the tags players give Moonbase Down on Steam (Indie, Action, Strategy, RPG, and Aliens): closest matches first, and among equally close ones the better-known games.

UFO 50
Shared: Indie · Action · Strategy

Notes of Soul
Shared: Action · Indie · Horror

Vampire Survivors
Shared: Indie · Pixel Graphics · Action Roguelike

Mount & Blade II: Bannerlord
Shared: Strategy · RPG · Action

Darkwood
Shared: Action · Survival Horror · Horror

Skul: The Hero Slayer
Shared: Indie · Action · Pixel Graphics

Ultimate Custom Night
Shared: Horror · Strategy · Survival Horror

Look Outside
Shared: RPG · Survival Horror · Pixel Graphics

The Escapists
Shared: Strategy · Indie · Pixel Graphics

Hades
Shared: Indie · Action · Action Roguelike

Party Hard
Shared: Strategy · Indie · Action

Hotline Miami
Shared: Action · Indie · Pixel Graphics

Zombie Night Terror
Shared: Strategy · Indie · Action

UnderMine
Shared: Indie · RPG · Action

Streets of Rogue
Shared: RPG · Action · Indie

Freeman: Guerrilla Warfare
Shared: Action · Strategy · RPG

Hero Siege
Shared: RPG · Pixel Graphics · Indie

The Last Spell
Shared: Strategy · RPG · Indie

At Dead Of Night
Shared: Strategy · Survival Horror · Horror

OMORI
Shared: Indie · RPG · Pixel Graphics

Bendy and the Dark Revival
Shared: Action · Indie · Horror

Tales of the Black Forest
Shared: Indie · RPG · Pixel Graphics

Lethal Company
Shared: Horror · Survival Horror · Indie

Chroma Squad
Shared: Strategy · RPG · Indie