Games like Zombie Survivors 1
Games like Zombie Survivors 1 include Yet Another Zombie Survivors, Megabonk, FatalZone, Brotato, and Nuclear Throne. We matched them by the tags players give Zombie Survivors 1 on Steam (Zombies, Action Roguelike, Bullet Hell, Top-Down Shooter, and Roguelike): closest matches first, and among equally close ones the better-known games.

Yet Another Zombie Survivors
Shared: Zombies · Action Roguelike · Top-Down Shooter

Megabonk
Shared: Action Roguelike · Roguelike · Bullet Hell

FatalZone
Shared: Action Roguelike · Bullet Hell · Zombies

Brotato
Shared: Bullet Hell · Action Roguelike · Roguelike

Nuclear Throne
Shared: Action Roguelike · Roguelike · Bullet Hell

BALL x PIT
Shared: Bullet Hell · Action Roguelike · Action

Vampire Survivors
Shared: Action Roguelike · Bullet Hell · Roguelike

Halls of Torment
Shared: Action Roguelike · Bullet Hell · Roguelike

Enter the Gungeon
Shared: Action Roguelike · Bullet Hell · Roguelike

The Last Stand: Aftermath
Shared: Zombies · Top-Down Shooter · Action Roguelike

Army of Ruin
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter

Soulstone Survivors
Shared: Action Roguelike · Bullet Hell · Roguelike

20 Minutes Till Dawn
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter

Death Road to Canada
Shared: Zombies · Action Roguelike · Roguelike

Project Zomboid
Shared: Zombies · Survival · Building

Apocalypse Party
Shared: Action Roguelike · Top-Down Shooter · Bullet Hell

Death Must Die
Shared: Action Roguelike · Bullet Hell · Roguelike

Tiny Rogues
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter

Hades
Shared: Action Roguelike · Roguelike · Action

Pathogenic
Shared: Bullet Hell · Roguelike · Top-Down Shooter

Left 4 Dead 2
Shared: Zombies · Action · Shooter

Hades II
Shared: Roguelike · Action Roguelike · Action

Hero Siege
Shared: Action Roguelike · Roguelike · RPG

Goobies
Shared: Action Roguelike · Bullet Hell · Top-Down Shooter