17'' screen can some of the time, is good enough for the laptop and desktop gaming. And the experience in such case that can be good enough in many ways. I'd say there does not seem to be anything perfect though. Some are happy with small screen too.
Yeah. I see your point but I agree on your statement that some are happy and contented playing in a small screen as well.
I prefer a minimum size of 4 inches, but I would much rather play games on a PC rather than on a phone.
I usually used bigger size screen while playing mobile games online. It is more convenient and easy to grip if I use a 5 - 5.5 inch phone.