These days ALL games are based on existing code of some sort, so all games are based in one way or another on 'middleware'. It lets you go right to what matters, without spending years to code everything from zero. So why game companies use middleware very often? Because it's the fastest, least expensive way to make a game. Not only you had Gamebryo, but also SpeedTree for vegetation, and the face middleware that produced that HORROR that was the faces. Gamebryo in particular was bad because of very bad memory management, and because Oblivion was layered with terrible middleware on top of each other. Some people will say that the scope of the games do not lend themselves to such an involved engine. The guns felt so good in wolfenstein, why can't that feeling be replicated with magic/swords? I want something with the engine of wolfenstein, but for first person magic/melee. It just doesn't feel visceral or affective. I don't believe anyone that tells me the combat is good in these games. It is very clear this engine is limiting. The minute I took control of my character, I knew, it was just an uprezzed oblivion. I told myself that it was going to be something new and fresh, or that the changes they made changes the jank. I was very excited for Skyrim, only to find out that it was on the gambryo engine. What we need to talk about: how much it sucks/how limiting it is, and how badly Bethesda need to use a new engine for the next installment of Elder Scrolls/Fallout. My experience with it started with Morrowwind and continued to Oblivion and Skyrim. If you don't know what it is, it is the game engine Bethesda has used for (what seems like) all of the modern 3d polygonal elder scrolls games.

Gamebryo engine.