I think frank hit the nail on the head with this one. I would like to add though, the unreal engine is extremely powerful and as developers we're in not really limited how we choose to have normals/specs are rendered out, or anything for that matter.
Unreal has an awesome material system that allows anyone to easily create a parallax effect if desired and/or adjust how powerful your spec is (among a massive amount of other possibilities). While Frank is able to adjust the rendering system through the code, artists have the ability to take it one step further utilizing the material system. Unreal defaults to the phong rendering shader and I believe thats one reason many games have similar appearances but there is nothing stopping you from say, making it look like Team Fortress 2 as I've already discovered
and still in the process of getting the rest posted up.