Due to the large volume of questions and comments concerning the Engine, we did not have a chance to respond to your post at the time you submitted it. However, if you are still interested, the following documentation lists both recommended hardware and minimum software requirements to run UE4 (which goes also for packaged UE4 games):
Hardware & Software Specifications
I would add that typically, a mid level to high GPU is going to be critical factor that not all end users are necessarily going to have.
-.