Games like Mob Marathon
Games like Mob Marathon include Vampire Survivors, Timberman, Superflight, Broforce, and Skul: The Hero Slayer. We matched them by the tags players give Mob Marathon on Steam (Action, Casual, Arcade, Side Scroller, and 2D): closest matches first, and among equally close ones the better-known games.

Vampire Survivors
Shared: Pixel Graphics · 2D · Casual

Timberman
Shared: Casual · Action · Pixel Graphics

Superflight
Shared: Casual · Action · Relaxing

Broforce
Shared: Action · Pixel Graphics · 2D

Skul: The Hero Slayer
Shared: Action · Pixel Graphics · 2D

Teenage Mutant Ninja Turtles: Shredder's Revenge
Shared: Side Scroller · Pixel Graphics · 2D

SANABI
Shared: Action · Pixel Graphics · 2D

Kung Fury: Street Rage - Ultimate Edition
Shared: Arcade · Action · Side Scroller

pureya
Shared: Casual · Arcade · 2D

A Dance of Fire and Ice
Shared: Arcade · 2D · Indie

DAVE THE DIVER
Shared: Casual · Pixel Graphics · Relaxing

UFO 50
Shared: Action · Pixel Graphics · Arcade

Streets of Rage 4
Shared: Action · 2D · Arcade

Shower With Your Dad Simulator 2015: Do You Still Shower With Your Dad
Shared: Arcade · Casual · 2D

Cyberhunt
Shared: Action · Casual · Arcade

Shelldiver
Shared: Casual · Arcade · 2D

Dino Run DX
Shared: Action · Arcade · Pixel Graphics

Rogue Legacy 2
Shared: Arcade · Action · Indie

Gensokyo Night Festival
Shared: Action · Casual · Pixel Graphics

Unpacking
Shared: Casual · Relaxing · Pixel Graphics

Rhythm Doctor
Shared: Pixel Graphics · Action · Indie

Exit the Gungeon
Shared: Action · Arcade · Indie

DJMAX RESPECT V
Shared: Casual · Action · 2D

Planes, Bullets and Vodka
Shared: Action · Casual · Arcade