I've actually just looked and there was a thread for this that's fully developed, but it no longer exists. Feel free to go ahead and add more lists here. I'll do mine!
Iron Maiden - Phantom of the Opera - how could it be anything else?
Killers - Killers - also a big fan of Murders and Prodigal Son, but Killers is heads and tails above the others.
The Number of the Beast - Hallowed Be Thy Name - NOTB is the other possibility.
Piece of Mind - Revelations - this one isn't even close.
Powerslave - Powerslave - one of my favourite songs, my favourite instrumental section. Aces High and Rime are also truly epic.
Somewhere in Time - Wasted Years - soooooooooooooooo understaaaaanaaanananaaaad
Seventh Son of a Seventh Son - The Evil That Men Do - an album I consider to be above average but with only one truly standout track.
No Prayer for the Dying - No Prayer For The Dying - a highly underrated song.
Fear of the Dark - Fear Of The Dark - better live, but still the best song on the album. Only ATSS comes close.
The X Factor - The Edge of Darkness - this is a fairly recent development, but I firmly believe this is Blaze's best Iron Maiden song.
Virtual XI - The Clansman - freedom!
Brave New World - Ghost of the Navigator - a true classic.
Dance of Death - Paschendale - the best Iron Maiden song, bar none. Their absolute climax in lyrical and musical storytelling.
AMOLAD - Brighter Than A Thousand Suns - a pure epic on an album with multiple pure epics.
The Final Frontier - Starblind - Bruce's best lyrics? I think so
The Book of Souls - The Book of Souls - The climax of a superb album. I can honestly say that this song goes to 11.