Well I listen to MJ and his lyrics and it's so child like, there's nothing deep about them. It's like reading a Fearstreet novel which would be for teens and then jumping to Mary Shelly's Frankenstein which it's clearly filled with more than just the simple story and conclusion. There is such a thing as simple not emotional music like MJ or Madonna.
Also when you have to point out that their pop artist that kinda sums up my view on them, their good in their respected genre but in the pantheon of great artist don't even mention them cause they don't cut.
Now the genius singers/musicians are clearly based of taste like your basing your geniuses. Like me you may disagree on that but to each his own.
I went a little overboard with the dancing part there lol but I honestly don't feel he has anything special with his voice. I mention a ton of singers from his era and they might not be able to sing in tune now or ten years ago but one is not measured past his prime but in his prime. So yes all those singers in their hey day blow MJ out of the water.
The mature sounding music thing is just me saying MJ has no depth emotionally nor lyrically. There's nothing in his music that sounds like a growth in him, he sounded the same to me in every era. I guess the one song would be Billie Jean.
My point is he did what he did but would you really put his voice next to Mercury's? Cause I for sure wouldn't.
His lyrics are far from child like. You must be listening to his love songs. Listen to "Is It Scary", "Threatened", "Ghost", or "Morphine". Those are all songs that have depth emotionally and have lyrically. Michael Jackson actually wrote. Again you should go back to listen to all of his albums before you claim he doesn't have "depth". You're just looking at a few songs, and not what the man was fully capable of doing music-wise.