Grand Illusion is their best album. But I have to put in a plug for Cyclorama. I also like Equinox, Crystal Ball, Pieces of 8, Paradise Theater and One With Everything
The Wooden Nickel albums are also fun to listen to from time to time.
I absoluteley don't like
Cornerstone
Kilroy
Brave New World
I don't own Edge of the Century
Their covers album has it's moments.