I'm interested in game engines so started looking into it further.
Here's a list of games, their engines and approx how many lines of code.

Thought I'd share on here as it's useful to know.
Allows people to manage their own expectations realistically when starting out!
(In my case I'm working on a game engine in C++)


The List
Sorted by Game Engine
Proprietary format is: Game Name (Engine Name) (Syntax) (Codebase Length)


Blender Game Engine
? (?) (?)

CryTek Engine
Star Citizen / Squadron 42 (?) (?)

id Tech
Doom (?) (C++) (?)

Source Engine (C++)
Half Life 2 (?) (?)
Team Fortress 2 (?) (?)
Dota 2 (?) (?)

Unity Engine (C#)
Interstellar Marines (?) (?)
Angry Birds 2 (?) (?)
Hearthstone (?) (?)
Space Hulk (?) (?)
Kerbal Space Program (?) (?)
The Flock (?) (?)

Unreal Engine (C++)
Aliens: Colonial Marines (?) (?)
Borderlands 2 (?) (?)
ARK: Survival Evolved (?) (?)
Day One: Garrys Incident (?) (?)

Proprietary Engines
World Of Warcraft (?) (C++) (10,000,000+)
Aliens vs. Predator (Asura) (C++) (?)
Sniper Elite (?) (C++) (?)
Sniper Elite V2 (Asura) (C++) (?)
Sniper Elite 3 (Asura) (C++) (?)
DayZ (?) (C++) (?)
Skyrim (?) (C++) (?)
Battlefield 3 (Frostbite) (C++) (?)
F1 2013 (Ego) (C++) (?)
Warframe (Evolution) (C++) (?)
Space Engineers (VRAGE) (C#) (?)
DCS World (?) (C++) (?)

I will keep adding to this over time.
Feel free to share others in the comments and I will add them

;o)