Which game engine are you using - Unity, CryEngine, UnrealEngine or maybe other?
And explain why are you using this engine?
I am using Unity3d because it has friendly interface, 2D and 3D mode, C# and Javascript scripts and free.
I think at present they're two engines with varying targets. That's not to say they couldn't target the same thing but I see CryENGINE as a much "heavier" engine for lack of a better word, whereas Unity is lightweight and better suited to certain types of game/platform (mobile, browser-based, etc). I can't compile a gameplay prototype for web release in under 2MB with CryENGINE for instance. At the same time, if I were developing an AAA shooter that needed* extremely shiny graphics, then Unity might not be my first port of call. I haven't seen a whole lot of Unity projects going in that direction however so I could be wrong there!