Games like Monsterland
Games like Monsterland include Bit Blaster XL, BALL x PIT, Nova Drift, Hollow Knight, and 12 is Better Than 6. We matched them by the tags players give Monsterland on Steam (Shoot 'Em Up, Top-Down Shooter, Difficult, Real-Time, and Shooter): closest matches first, and among equally close ones the better-known games.
Bit Blaster XL
Shared: Shoot 'Em Up · Difficult · Shooter
BALL x PIT
Shared: Shoot 'Em Up · Arcade · Top-Down Shooter
Nova Drift
Shared: Shoot 'Em Up · Arcade · Shooter
Hollow Knight
Shared: Difficult · 2D · Indie
12 is Better Than 6
Shared: Top-Down Shooter · Shooter · Action
ZeroRanger
Shared: Shoot 'Em Up · Arcade · Shooter
Hollow Knight: Silksong
Shared: Difficult · 2D · Indie
Ikaruga
Shared: Shoot 'Em Up · Arcade · Difficult
Bot Vice
Shared: Top-Down Shooter · Shoot 'Em Up · Difficult
Nuclear Throne
Shared: Difficult · Roguelike · Top-Down Shooter
The Binding of Isaac: Rebirth
Shared: Difficult · Roguelike · Indie
Nine Sols
Shared: Difficult · 2D · Action
DoDonPachi Resurrection
Shared: Shoot 'Em Up · Top-Down Shooter · Shooter
Zombotron
Shared: 2D · Shooter · Shoot 'Em Up
Exit the Gungeon
Shared: Arcade · Difficult · 2D
Chippy
Shared: Shoot 'Em Up · Top-Down Shooter · Difficult
Star Saviors
Shared: Shoot 'Em Up · Arcade · Action
SYNTHETIK: Legion Rising
Shared: Top-Down Shooter · Difficult · Shooter
LUFTRAUSERS
Shared: Shoot 'Em Up · Arcade · 2D
Rogue Legacy 2
Shared: Arcade · Difficult · Action
Cyberhunt
Shared: Shoot 'Em Up · Arcade · Action
Spelunky
Shared: Difficult · Roguelike · 2D
Skul: The Hero Slayer
Shared: Roguelike · 2D · Action
Revolution Ace
Shared: Shoot 'Em Up · Shooter · Arcade