To each his own and all of that but,
I find it silly when a band write a bunch of songs and then just writes separate lyrics but kinda sorta on the same theme and the calls it a concept album (*cough* isolate *cough* -adore the album though!)
A concept album to me is like Operation: Mindcrime or DT's SFAM, when everything was thought through from the beginning and written to tell a tale.
The first type is not bad in any way, but from my perspective inferior as it lacks the extra dimension that comes in when the music was originally written to convey a certain message and designed to fulfill that specific purpose.
At least, again from my humble perspective, if there isn't a continuous story it is not a concept album, and if there are no like repeated themes, ryhtms or riffs etc and the music wasn't written for a certain purpose, it is simply inferior.
Now more on-topic, here are my faves:
-Blind Guardian - Nightfall in Middle-Earth
-Dream Theater - Scenes from a Memory
-Queensryche - Operation: Mindcrime
-Iron Maiden - Seventh Son of a Seventh Son (although that hardly fulfills my rules from earlier in the post, but hey, Maiden is always gonna be Maiden for me...)
-Mind's Eye - A Gentleman's Hurricane
-Symphony X - V
