What's the best game engine?

Depends on the scope. Unity3d is the best when it comes to variable scope. Boilerplating is all but done and you just code away in c#. Unreal's c++ is more advanced, unreal's blueprints get very messy if you're doing anything complex. Cry engine is dead. Lubmeryard is stuck in perpetual beta. And there is also an avalanche of smaller engines around.

Liek - you can even dig out ogre and have a go with it...if you hate yourself that is.