In the realm of the 15``, the Asus N550JV will be a good choice (I have the same but with a touch screen which is a little more expensive than this one)(I'm able to play games on high/sometimes ultra without problems) http://www.xoticpc.com/asus-n550jvdb71-p-6115.html
If he wants to get a slimmer pc with the same specs and willing to pay a little more money (which I think he can if he wanted to buy a macbook pro), then there is the XPS 15. http://www.dell.com/us/p/xps-15-9530/pd