And with the release of FIFA 19, I officially end the comparison. FIFA 18 has sold the most in one year, though at the current rate of sales considering FIFA 19 will eat all future sales, Skyrim will no doubt beat it. It's been a surprisingly close match, with Europe giving FIFA the most sales, North America supporting Skyrim the most, the tiebreaker ended up being Japan here. The digital sales are not accounted here, though it's pretty clear FIFA has the advantage of those as well, considering the multiple sales it has had.
You know it deserves the GOTY.