This is the most unquestionably difficult ranking I could undertake. The # of albums I consider borderline flawless from each of these bands is ridiculous. Over a dozen albums from these 3 bands have legitimate arguments to be considered the greatest traditional heavy metal album of all time.

I have a few rankings that are likely hot takes here
** Yes, I like Dance of Death more than most folks. Title track and Paschendale are both top 10 Maiden songs, and Montsegur is only a small step behind that. Those 3 songs are better than anything on Brave New World to me, but the rest of BNW is better and higher quality.
** Yes I kinda like Turbo. It's silly but it's fun and the guitar work and Rob's vocals are absolutely stellar. That kinda sucks about Ram It Down, it's got some of Priests' best lead guitar work and I don't think Rob ever sounded better, but dear lord, some of those songs...
As for the top 6 albums here, honestly put them in whatever order you want. They're that close to me and mood depending it could change