1080p / 1440p are what most people use and esport titles usually can run really high fps without having to buy right at the top end , I myself rather stick to 1440p I get more bang for buck from GPU dont see point of 4K for gaming unless you wanna play on large screen I prefer playing on desk with monitor infront so dont need massive screen
unless you have money to burn the 30 series didnt give much headroom at 4K unless FPS is well north of 100fps I aint interested in 4K
a lot of games unfortunately are CPU bound at 1080 and 1440 so even if you have a top of the line GPU you can't always utilise it