Ultimately, it depends on what you want to accomplish with the discussion. If you just want to say your console has the most exclusives, most fans of Sony/Nintendo prefer to not count ones with PC ports. If you actually want to stack a console's library vs competitors, you should include anything not available on competing platforms.
Taking games like Titanfall/Planetside, for instance:
Titanfall is exclusive to the Xbox platform. It's an Xbox exclusive, but not an X1 exclusive. But it should be on any exclusive list, as it is not on any COMPETING platform.
Planetside is on PC, but PC is only bearly competing with consoles - generally people have a preferance, and they make most of their purchases for it. So it should also be on exclusive lists.
