You are making the same mistake that the majority of Apple defenders make, namely that a metal casing = high build quality. I own plenty of cheap items made from metal, and of varying build quality. Build quality takes in many factors; such as fit & finish, button quality, longevity of individual components etc and it also takes quality control into consideration; which should pick up issues such as light bleed, yellow screen tint, dead pixels, scratches and scuffs etc.
I would go so far as to say that iPhones actually have *poor* build quality. These things are churned out, built to maximise profits, corners are cut and quality control appears to be non-existant. It's a complete lottery as to whether you receive a good one, and even then you will be dealing with a cheaply made phone. Face it, iPhone quality has plummeted since the 4/4S. The 5 and 5S held onto a good part of the old quality, but the iPhone 6 has kissed it goodbye. This feels like a new era for Apple, and I'm not liking it one bit. Cheaply made, low-spec phones with bug-ridden software are not good enough for me.