The answer is always "it depends". We need to know what you want to do with it to give a real answer. Gaming?, HD, QHD, 4K ? 60 fps good enough or you are shooting for 144fps because you're into e sports, what's the deal. Sorry but there are way too many questions asked like this with no real info to go on.
Anyway just to play games and have an enjoyable experience all you really need is an i5 or ryzen 5 and a 1070, if you want to spend more than that then go for a better graphics card, and if you still want to spen more or really are aiming for those crazy high frame rates then go for the i7.
Bear in mind intel is rumoured to be releasing 8 core CPUs very soon, and Nvidia just released the RTX series although they seem too expensive...