Controversial opinions on metal

The first five are all excellent. Of the three with Bruce I'd probably put NOTB at the bottom, but just barely.

Somewhere in Time was their first noticeable step down. Still a great album, but that's when the choruses started to get repetitive, and the vocals sound a bit worn out/flat compared to the earlier ones. The leads are actually the highlight of the album on the whole, only a few excellent songs.
 
What's everyone's opinion on Number of The Beast?

I really like that album. Not my favorite, but definitely in my personal top three. Along with Powerslave and Seventh Son.

Never really got into any other albums of theirs outside of those three, actually...Somewhere In Time I thought was fucking awful.

Piece of Mind should be your next stop. It's a better album than Number of the Beast imo. Where Eagles Dare and Die With Your Boots On are two of my fave Maiden tracks.
 
The first three Iced Earth albums are definitely underrated by certain trve el33t types, but not better than prime Maiden.
 
First three albums are better than anything Iron Maiden has done in my opinion, Horror Show is also good but not better than Iron Maiden, Dystopia was decent I should listen it again.
 
I have no idea how people can pick 10 albums as their "favorites" there's literally no way I could possibly decide on something like that.