To dismiss games wholesale as "not exclusive" on the Xbox because they can also be played on the PC is pretty disingenuous. Not everybody has or wants a PC, not everybody that has one has a good gaming PC, and not everybody that has a good gaming PC actually prefers gaming on a PC over a console.
To the majority of people, the likes of Forza, Forza Horizon, Halo, Gears, Quantum Break, Ryse, Titanfall, Ori, Sunset Overdrive etc ARE exclusive to the Xbox, quite simply because they cannot be played on the PS or Nintendo.