Unreal uses FBX. 

http://udn.epicgames.com/Three/FBXAnimationPipeline.html

So if you have Poser game dev, then Poser figures should be usable because it exports to FBX. They don't have to be reduced res to work in the engine. 

 

Here is an example of Unreal Engine 4's real time rendering:

https://www.youtube.com/watch?v=dO2rM-l-vdQ

Say what you want, but I've never seen firefly produce anything close to that. 

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Cinema 4D is a modelling program as well as a 3D renderer, so Unreal isn't as much a threat to Cinema 4D as it is to Poser

Unreal and Unity both have modelers, tho it's an extra cost for Unity, unless you have a subscription to the full version or have bought the full license, but Unreal's modeler is built in. Probably isn't that great for organics, but it's plenty for architecture. Build, rig, texture all right there in the UDK.