From the top of my head, these are the songs that aren't based from top to bottom on E minor. As there are loads of variations on the songs, even on the E minor songs there are places in the song which switches to other tonalities and never get back to its original key. People here in the forum with more theorical knowledge than I have (mine is really empirical) can correct what's wrong and fill what's missing:
Burning Ambition
Iron Maiden
Invasion
Murders In The Rue Morgue
Another Life
Genghis Khan
Innocent Exile
Prodigal Son
Purgatory
Drifter
Twilight Zone
Invaders (starts in E, main riff is in A, bridge in B major, chorus in Eb)
The Prisoner
The Number Of The Beast
Run To The Hills
Gangland (modulates to A)
Total Eclipse
Revelations
Flight Of Icarus
Die With Your Boots On
Still Life
Sun And Steel
To Tame A Land (lot of variations)
Aces High
2 Minutes To Midnight
Losfer Words (Big 'Orra)
Flash Of The Blade
Back In The Village
Powerslave
Sea Of Madness (modulates to A, then B on the solo)
Heaven Can Wait
The Loneliness Of The Long Distance Runner (similar case to Aces High)
Déjà-Vu
Sheriff Of Huddersfield
Infinite Dreams (modulates a lot, too)
Can I Play With Madness
The Prophecy
The Clairvoyant
Only The Good Die Young
Tailgunner
The Assassin
Hooks In You
Mother Russia
Be Quick Or Be Dead
Afraid To Shoot Strangers
Childhood's End
The Fugitive
The Apparition
Judas Be My Guide
Weekend Warrior
Fear Of The Dark
Lord Of The Flies
Man On The Edge
The Aftermath
Judgement Of Heaven
2 A.M.
The Unbeliever (some odd harmonies)
Justice Of The Peace (modulates a lot)
Judgement Day
The Angel And The Gambler
Lightning Strikes Twice
The Clansman
When Two Worlds Collide
Don't Look To The Eyes Of A Stranger
Como Estais Amigos
Ghost Of The Navigator
Brave New World
Dream Of Mirrors
The Fallen Angel (modulates on the solo)
The Thin Line Between Love And Hate
Wildest Dreams
Rainmaker
No More Lies
Montségur (modulates to major tones on the second chorus)
Gates Of Tomorrow
New Frontier
Paschendale (modulates a lot)
Age Of Innocence (an odd harmony)
Journeyman
Brighter Than A Thousand Suns (starts in E, but has some variations)
The Legacy
El Dorado (stats in E, then goes C# on the bridge and G on the chorus, A on Smith's solo, E on Dave's solos and B on Jan's solo)
Mother Of Mercy
The Alchemist
Isle Of Avalon (E major, then E augmented then A on the intro, but the main chords of the song are in E minor)
Starblind (has lots of variations like E to G on the second chorus, D, F, then D on the melody after Jan's solo)
The Talisman
The Man Who Would Be King (has variation to E major)