In my opinion, the best album cover is A Dramatic Turn of Events.
It's a very good album, yet sadly so underrated. It contains some of my favorite Dream Theater songs, like Trial of Tears and Take Away My Pain. Trial of Tears especially is one of the best songs ever, because it has such an expressive lyrics and an awesome bass line. That song, in my opinion, is John Myung's masterwork.
Metropolis Pt. 1. My all-time favorite Dream Theater song, it would be the perfect ending for a concert.