The game engine is a library that simplifies creation of games. It could be limited to just creating easy-to-use wrappers over system interfaces such as graphics api, user control inputs and audio (SDL, ZenGL) as well as add additional interfaces to create and control the game content environment (Castle Game Engine). You can read more here
Here's a list of game engines that are Pascal/Delphi based or have Pascal binding libraries.
|Castle Game Engine||http://castle-engine.sourceforge.net/||FPC|
|Dan Jet X||wiki.mirgames.ru/danjetx (Rus)||Delphi|
|GameMaker: Studio||www.yoyogames.com||N/A||Yes, it's not really a game engine library. But it's a game engine and studio written in Delphi. Special Pascal proud.|