Moving Pictures
This is the perfect storm album. As in they had perfected all aspects of their craft, including managing how they produced LP's. It's also the album I have listened to most, and as one fellow posted, it's a great demo LP for your system. In my mind, you could dial your system (gear choice) specifically to this album. You don't have the right system until this album sounds glorious. But I listen to classic rock mostly, so I'm a little biased.
2112 is creatively my favorite album. I think part of the reason for this, with me, is similar to your first kiss. I had their early albums, but this album was when my mind exploded and I thought these guys were one of the top bands in the world. Plus, the album creates a soundscape that is unique and timeless. All these years later, I can listen to this and the thought of how many decades have passed eludes me.