The scale of completion that they have doesn't really apply to lots of games... You can't "beat" Audiosurf, you can't "beat" SimCity 2000, you can't "beat" Team Fortress 2, etc.
And they should at least put in two "unfinished" ranks, because I don't feel like Final Fantasy 10, in which I've beaten pretty much everything except the final boss, belongs in the same category as Spear of Destiny, which I've barely touched.
For games you cannot beat you put Null... And yes games you have not finished go to unfinished. And if FFX mattered so much you would say you beat it. Close enough.