An egregious oversight....so far, after perusing two pages worth.....Seventh Wonder "Mercy Falls".
The problem, though, is I can come up with 20 or more albums that all deserve to be pretty high on this list. Where do you draw the line?
For me the defining characteristic is longevity in rotation.
I still listen to ALL the albums I listed in my top 3 and runners up regularly. There are at least 20 more concept albums I listen to semi-regularly, like the rest of Neal Morse's solo catalog, which other than his first two solo records, are all concept albums. What's that, like 25 albums right there?
Mercy Falls would probably make it into my "top 25 concept albums' along with stuff from Pain of Salvation, Hourglass, Ayreon, Beardfish, Daydream XI, Dominici, Blaze Bayley, Fates Warning, Heart of Cygnus, Rush, Glass Hammer, Mercyful Fate, Megadeth, Shadow Gallery, The Tangent, Theocracy, Threshold, Vanden Plas