That's a good question really. Because, well:
1. If the album really is THAT good, then surely I would be listening to it already.
3. Whatever the causation, there is a ridiculous high correlation between albums I like and how much I listen to them.
2. For the past 2 years I have actively searched for new music to such an extent that I have hardly listened to any of my good ol'favourites. So this could just become a list of my old favourites.
Blind Guardian - A Night at the Opera :I was really into power metal in my mid-teenager years, and this is the one that stuck with me. Hansi's voice is just out of this world.
Dimmu Borgir - Puritanical Ephoric Misantropia: The only black(ish) metal album I could bear at the time. So much symphony. So much awesome.
Pain of Salvation - The Perfect Element: Perfect from start to finish, yet I haven't listened to it in an obsessive manner for 2-3 years.
Evanescence - Origin: It's not an album, strictly speaking
Within Temptation - Mother Earth: My first favourite metal album. Sadly, it has disappeared in the amount of music I have discovered since, but it's just as awesome as it was back then.
Honorable mentions: Eternal Tears of Sorrow - Before the Bleeding Sun, Pre-2005 Sonata Arctica and Nightwish, Stuff by Arjen Lucassen and by Hans Zimmer, Therion - Gothic Kabbalah