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For me they would be:
Paradox Development Studio
The Creative Assembly
Platinum Games/Capcom Clover
EAD
Monolith Soft
Edit: Since there seems to be some confusion in the posts:
Video Game Developer: A video game developer is a software developer (a business or an individual) which creates video games. A developer may specialize in a certain video game console (such as Nintendo's Wii U, Microsoft's Xbox 360, Sony's PlayStation 3), or may develop for a number of systems (including personal computers)
Video Game Publisher: A video game publisher is a company that publishes video games that they have either developed internally or have had developed by a video game developer.
Game Engine: A game engine is a system designed for the creation and development of video games. The leading game engines provide a software framework that developers use to create games for video game consoles and personal computers. The core functionality typically provided by a game engine includes a rendering engine (“renderer”) for 2D or 3D graphics, a physics engine or collision detection (and collision response), sound, scripting, animation, artificial intelligence, networking, streaming, memory management, threading, localization support, and a scene graph. The process of game development is often economized, in large part, by reusing/adapting the same game engine to create different games, or to make it easier to "port" games to multiple platforms.
Paradox Development Studio
The Creative Assembly
Platinum Games/Capcom Clover
EAD
Monolith Soft
Game development studio not cinematic set piece with tacked on gameplay development studio. 
Edit: Since there seems to be some confusion in the posts:
Video Game Developer: A video game developer is a software developer (a business or an individual) which creates video games. A developer may specialize in a certain video game console (such as Nintendo's Wii U, Microsoft's Xbox 360, Sony's PlayStation 3), or may develop for a number of systems (including personal computers)
Video Game Publisher: A video game publisher is a company that publishes video games that they have either developed internally or have had developed by a video game developer.
Game Engine: A game engine is a system designed for the creation and development of video games. The leading game engines provide a software framework that developers use to create games for video game consoles and personal computers. The core functionality typically provided by a game engine includes a rendering engine (“renderer”) for 2D or 3D graphics, a physics engine or collision detection (and collision response), sound, scripting, animation, artificial intelligence, networking, streaming, memory management, threading, localization support, and a scene graph. The process of game development is often economized, in large part, by reusing/adapting the same game engine to create different games, or to make it easier to "port" games to multiple platforms.
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