I totally agree with your definition of "inspiration" as opposed to "copying"/"citation".
But you're not grasping my point. What I'm trying to say is that NT didn't just copy it because they couldn't come up with something new. They are explicitly making it look more than 80% similar because they want to citate it. The difference is that, when you citate something (and not just copy it), you do it so the reference is clear, because you exactly want people to think of the original (which must be recognized as a piece of art, obviously). This is considered something valuable, if it is in small doses (just a picture in the entire game, not the whole game).
The same could be said for Vergil's mask, which clearly reminds us of that of V for Vendetta.
Or, to take an example from literature, the poem "In morte del fratello Giovanni". This poem is clearly inspired by Catullus's carmen 101, and it even reports carmen 101's last line. Now, the fact that Foscolo cited Catullus is not seen as lack of originality, but of great culture.
That is why citing is not just like copying. Citing is inserting a acculturated reference in an original work, while copying is just, well, copying without originality.