IMO the genre is not a good level of analysis for this particular debate. Metal music might have many components that Maiden carries, but also Maiden has many things that go beyond the sound of mainstream metal music.
A highly un-metal friend of mine just listened to FoI, and her reaction was like, "wtf this vocal is shouting and his highs are all over the place and so on!!!"
What she doesn't like was clearly the drama of Iron Maiden, such as these moments that Bruce does not simply try to sing according to the rules, but gives his voice to the characters that are supposed to say the words
passionately-- "in the name of God my father I fly!!". This is what makes Bruce's performances so surprising to me, but the outsiders may not like it. (who cares?
)
Of course, I had to explain to her that Bruce is one of the most capable singers of all time, and what she does not like is probably, if that's the right word, the
energy of his music. In the next attempt, I played Revelations, since I believe it would be an easier song for her to get used to the Maiden sound. Expectedly, she just loved the melodies and the way Bruce sings it.
I believe anyone can love Maiden--at least some snapshots from it. But the key is to find the right gate to enter the 'intersected worlds' of it.