So I am reasonably satisfied with the results.
About half the non-Maiden top ten would be in my top 10 and the others are worthy choices.
And I am perfectly happy with the number one choice.
Oddly enough, the most overrated album on there is a Maiden album: Seventh Son, which is no more than middle of the pack on my Maiden list, and not a top 10 contender at all.
My list of top 20 essential albums that were in the game (off the top of my head, in order of release) is very skewed to early '80s metal:
Thin Lizzy — Jailbreak
Blue Oyster Cult — Spectres
AC/DC — Back in Black
Judas Priest — British Steel
Black Sabbath — Heaven and Hell
Rush — Permanent Waves
Black Sabbath — Mob Rules
Judas Priest — Screaming For Vengeance
Rush — Moving Pictures
Dio — Holy Diver
Iron Maiden — Number of the Beast
Iron Maiden — Piece of Mind
Judas Priest — Defenders of the Faith
Rush — Grace Under Pressure
Iron Maiden — Powerslave
Iron Maiden — Somewhere in Time
Queensryche — Operation Mindcrime
Saxon — Unleash the Beast
Halford — Resurrection
Iron Maiden — The Final Frontier