Games like Halloween Forever
Games like Halloween Forever include Alex Jones: NWO Wars, Anomaly Agent, Huntdown, Broforce, and METAL SLUG. We matched them by the tags players give Halloween Forever on Steam (Side Scroller, Hack and Slash, 2D Platformer, Shoot 'Em Up, and Platformer): closest matches first, and among equally close ones the better-known games.

Alex Jones: NWO Wars
Shared: 2D Platformer · Side Scroller · Shoot 'Em Up

Anomaly Agent
Shared: Side Scroller · 2D Platformer · Hack and Slash

Huntdown
Shared: Side Scroller · Shooter · Shoot 'Em Up

Broforce
Shared: Platformer · 2D · Side Scroller

METAL SLUG
Shared: Side Scroller · Arcade · Shoot 'Em Up

Pizza Tower
Shared: 2D Platformer · Platformer · Funny

Contra: Operation Galuga
Shared: 2D Platformer · Side Scroller · Platformer

Katana ZERO
Shared: Platformer · 2D Platformer · Hack and Slash

Guns, Gore & Cannoli
Shared: Side Scroller · Shoot 'Em Up · 2D

Kero Blaster
Shared: Side Scroller · Shoot 'Em Up · Platformer

Momodora: Reverie Under The Moonlight
Shared: Side Scroller · 2D Platformer · 2D

Terminator 2D: NO FATE
Shared: Side Scroller · 2D Platformer · Arcade

Super Meat Boy
Shared: Platformer · 2D Platformer · 2D

METAL SLUG 3
Shared: Side Scroller · Arcade · Shooter

Nitro Express
Shared: Side Scroller · 2D Platformer · Shooter

SHINOBI: Art of Vengeance
Shared: 2D Platformer · Platformer · Hack and Slash

Warhammer 40,000: Shootas, Blood & Teef
Shared: Side Scroller · 2D Platformer · Shoot 'Em Up

Have a Nice Death
Shared: Hack and Slash · 2D Platformer · 2D

Skul: The Hero Slayer
Shared: 2D · Platformer · Side Scroller

Guns of Fury
Shared: Platformer · Shoot 'Em Up · Shooter

pureya
Shared: Arcade · Side Scroller · 2D

Missing Banban
Shared: Side Scroller · 2D Platformer · Shoot 'Em Up

NINJA GAIDEN: Ragebound
Shared: 2D Platformer · Side Scroller · Platformer

Blazing Chrome
Shared: Side Scroller · Shoot 'Em Up · Arcade