You do have more exposure to music than the average person though right?
On the other point, I don't see why MJ shouldn't be classified as a musical genius, or why he couldn't be. Musicians have different strengths. What's important is they have a strength they capitalize on, and MJ had multiple that he utilized to his advantage. Everyone has a different idea of good musicianship. For a long time, I didn't appreciate Mozart, thinking his music emotionless and uninspired, but my opinion has since changed because what I want from music has changed.
I think a lot of people don't think MJ's a "musical genius" because there's no evidence showing he's a great instrumentalist or lyricist, but those aren't the only things that contribute to good music. Songwriting is as much about lyrics and instrumental skill able
to wielded as it is creating good combinations to form interesting soundscapes and having a good sense of rhythm.
He's also superior to someone like Lennon, McCartney, and Dylan in singing ability. As a tween, he has a great range with excellent precision of pitch.