The only game I play Windowed on the desktop is Heroes of Might and Magic 2. If you fullscreen that shit you have pixels the size of a Halfling fist, that just doesn't work
As for the commentary of sticking to 1080p~ish monitors because performance... I don't know guys, try it and be amazed. Resolution up isn't as big a performance killer as you might think. Quality level up kills perf, resolution not quite as much... I did play @ 3440x1440 even on a GTX 1080 and at medium~high settings virtually everything except new AAA was perfectly playable, as in >50 FPS and much higher.
Still wouldn't advocate moving to 4K 16:9 though... if you want to step up from 1440p, get the ultrawide version, horizontal view expansion is awesome and 21:9 doubles as that dual monitor setup you used to have, WIN key plus directional is your new friend. Two full height web pages side by side... glorious.