Hopped on this launch trailer with game engine guru Jerry O'Flarity.
Both Jerry and Vernon Wilbert are industry experts at knowing how to properly use game engines for cinematic and story telling purposes. This is opposed to their original use - making 3D game levels. Engines have had a long history of also being used for lower end, "in game" quality cinematics but new technologies such as the Unreal 3 Engine and CryEngine Cinebox are now getting so sophisticated they're evolving into cinema tools capable of creating high end "game plus" machinima pieces.
Game engines can have a very long learning curve and are often incredibly challenging to import/export rigs and animation out of. Since everything in engine needs to be in real time (the engine scenes are what the gamer is eventually playing) optimization is key as textures, lighting, shading, fx, etc, are all in a single 3D scene.
On a previous engine job we had undertaken the client was adamant about all elements being done in engine. This was so they could say the trailer was the exact same quality level as the game play but still with the "game plus" look. It ended up being one of the most difficult spots the team had ever worked on and multiple people had melt downs.
Jerry's technique on this job was to do the opposite and strip out everything except environment and characters and let all the elements and polishing be done in comp. Fx & simulation is completely different every time in engine which makes it nearly impossible to control. Doing it this way give full control and saved us major time. All in a great Image Comic style.