No single game really is but it adds to the attraction along with others. The choice for console buying (for most) comes down to what games it has so adding another to the list 'not on PS4' is a win for MS even if a small one.
I bought an X1 because I was interested in the hardware more than a PS4 - i'm not really a big console gamer anyway. Don't have kids therefore disposable income
I haven't owned a console since the SNES. I bought a second hand PS3 just to play The Last of Us, spent the best part of a week banging into everything/looking at the floor/sky, as I hadn't picked up a controller since my SNES days. Ended up having to play with aim assist on and difficulty on easy as my brain/hands just could not get used to no keyboard/mouse - still enjoyed it for the experience though!
Gave the console & game to charity once I finished - thus began and ended my dabble into the modern console