Games like Area 51 Defense
Games like Area 51 Defense include RUINER, Hotline Miami, The Ascent, Trepang2, and My Friend Pedro. We matched them by the tags players give Area 51 Defense on Steam (Action, Indie, Violent, Isometric, and Shooter): closest matches first, and among equally close ones the better-known games.

RUINER
Shared: Action · Indie · Violent

Hotline Miami
Shared: Action · Violent · Indie

The Ascent
Shared: Action · Top-Down Shooter · Shooter

Trepang2
Shared: Shooter · Action · Violent

My Friend Pedro
Shared: Action · Indie · Shooter

Bright Memory: Infinite
Shared: Action · Indie · Shooter

PUBG: BATTLEGROUNDS
Shared: Shooter · Survival · Action

Ready or Not
Shared: Shooter · Action · Horror

Guardians of Orion (Phase 2)
Shared: Action · Indie · Shooter

12 is Better Than 6
Shared: Action · Shooter · Indie

Alien Shooter
Shared: Action · Shooter · Horror

DOOM Eternal
Shared: Action · Violent · Shooter

Hotline Miami 2: Wrong Number
Shared: Action · Violent · Indie

Shadowgrounds
Shared: Action · Top-Down Shooter · Shooter

Dead Space™ 3
Shared: Action · Horror · Shooter

Dead Space™ 2
Shared: Action · Shooter · Horror

Left 4 Dead 2
Shared: Action · Shooter · Survival

Black Mesa
Shared: Action · Shooter · Sci-fi

Bean Battles
Shared: Action · Indie · Violent

Shadowgrounds Survivor
Shared: Action · Shooter · Isometric

SUPERHOT
Shared: Action · Indie · Shooter

SYNTHETIK: Legion Rising
Shared: Indie · Action · Top-Down Shooter

CARRION
Shared: Action · Indie · Violent

Call of Duty®
Shared: Action · Shooter · Violent