The game engine stats outlines the most popular game servers

Game Name Engine
Game Name Engine
7 Days to Die Unity 3D
Action Half-Life GoldSrc
Action: Source Source
American Truck Simulator prism3d
ARK: Survival Evolved Unreal 4
ARMA 3 Real Virtuality 4
Arma Reforger Enfusion
Assetto Corsa Unity 3D
Avorion None
Ballistic Overkill Unity 3D
Barotrauma None
Base Defense GoldSrc
BATTALION: Legacy Unreal 4
Battlefield 1942 Refractor
Battlefield: Vietnam Refractor
Black Mesa: Deathmatch Source
Blade Symphony Source
Brainbread GoldSrc
BrainBread 2 Source
Call of Duty idtech3
Call of Duty 2 iw2.0
Call of Duty 4 iw3.0
Call of Duty: United Offensive idtech3
Call of Duty: World at War iw3.0
Chivalry: Medieval Warfare Unreal 3
Codename CURE Source
Colony Survival Unity 3D
Core Keeper Unity 3D
Counter-Strike GoldSrc
Counter-Strike: Condition Zero GoldSrc
Counter-Strike: Global Offensive Source
Counter-Strike: Source Source
Crafting Dead Unity 3D
Craftopia Unity 3D
Day of Defeat GoldSrc
Day of Defeat: Source Source
Day of Dragons Unreal 4
Day of Infamy Source
DayZ (Experimental) Enfusion
Deathmatch Classic GoldSrc
Don't Starve Together None
Double Action: Boogaloo Source
Dystopia Source
Eco Unity 3D
Empires Mod Source
ET: Legacy idtech3
Euro Truck Simulator 2 prism3d
Factorio None
Fistful of Frags Source
Garry’s Mod Source
Half-Life 2: Deathmatch Source
Half-Life Deathmatch: Source Source
Half-Life: Deathmatch GoldSrc
Hurtworld Unity 3D
HYPERCHARGE: Unboxed Unreal 4
Insurgency Source
Insurgency: Sandstorm Unreal 4
IOSoccer Source
Jedi Knight II: Jedi Outcast idtech3
Just Cause 2 Avalanche
Just Cause 3 Avalanche
Killing Floor Unreal 2
Killing Floor 2 Unreal 3
Last Oasis Unreal 4
Left 4 Dead Source
Left 4 Dead 2 Source
Medal of Honor: Allied Assault idtech3
Memories of Mars Unreal 4
Minecraft: Bedrock Edition None
Minecraft: Java Edition lwjgl2
Mordhau Unreal 4
Multi Theft Auto Renderware
Mumble None
Natural Selection GoldSrc
Natural Selection 2 Spark
Necesse None
No More Room in Hell Source
NS2: Combat Spark
Nuclear Dawn Source
Onset Unreal 4
Operation: Harsh Doorstop Unreal 4
Opposing Force GoldSrc
PaperMC lwjgl2
Pavlov VR Unreal 4
Pirates, Vikings, & Knights II Source
Post Scriptum Unreal 4
Project Cars Madness
Project CARS 2 Madness
Project Zomboid lwjgl2
Quake 2 idtech2
Quake 3: Arena idtech3
Quake Live idtech3
Quake World quake
Red Orchestra: Ostfront 41-45 Unreal 2
Return to Castle Wolfenstein ioquake3
Ricochet GoldSrc
Rising World None
Rust Unity 3D
San Andreas Multiplayer Renderware
Satisfactory Unreal 4
SCP: Secret Laboratory Unity 3D
SCP: Secret Laboratory ServerMod Unity 3D
Soldat None
Soldier of Fortune 2: Double Helix Gold idtech3
Source Forts Classic Source
Squad Unreal 4
Starbound None
Stationeers Unity 3D
StickyBots Unreal 4
Survive the Nights Unity 3D
Sven Co-op GoldSrc
Team Fortress 2 Source
Team Fortress Classic GoldSrc
Teamspeak 3 None
Teeworlds None
Terraria None
The Isle Unreal 4
The Specialists GoldSrc
Tower Unite Unreal 4
Unreal Tournament Unreal 4
Unreal Tournament 2004 Unreal 2
Unreal Tournament 3 Unreal 3
Unreal Tournament 99 Unreal
Unturned Unity 3D
Valheim Unity 3D
Vampire Slayer GoldSrc
Velocity Proxy lwjgl2
Vintage Story None
Warfork Qfusion
WaterfallMC lwjgl2
Wolfenstein: Enemy Territory idtech3
Wurm Unlimited None
Zombie Master: Reborn GoldSrc
Zombie Panic! Source Source