Have you already got an xbox one (none x)? if so you can just do your backwards compatibility on there and play the better xbox one x games on pc if you upgrade to a 1080. If you don't have an xbox one at all then I can see the "x" making more sense. My advice would be wait till later in the summer, NVidia and amd should have new cards out by then so the leap might be bigger than if you buy now, plus the gap between those and the "x" will be much larger.
Gran turismo for me, they basically stopped doing anything to the base game after 2. The ui is stupid, the cars don't look good, the opponent ai is also bad. It's pretty much a caricature of it's self these days