Recently I've been giving a few more listens to the RoadRunner albums (the ones I grew up with after I discovered the band). I think I rank them like this right now:
1 Dream Theater - still my favourite album (by any band), but at any moment it could be defeated by...
2 The Astonishing - I can't get enough of it. The longest album I've ever listened to, but it still feels short. So much fun here.
3 Systematic Chaos - I'm surprised at how much I've enjoyed it recently, after years of ignoring it.
4 Black Clouds & Silver Linings - only thing that bugs me about this one is the lack of JM, both mix-wise and the fact that he only gets one spotlight moment in the whole album.
5 A Dramatic Turn Of Events - great album, which for some reason I didn't care about when it was released (I was still in my 'no MP no DT' phase)
As for the others, I think this would be it:
1 Six Degrees Of Inner Turbulence - the one with which I fell in love with the band in 2006.
2 Images & Words
3 Falling Into Infinity
4 Scenes From A Memory
5 Train Of Thought
6 Awake
7 Octavarium
I can't rank the debut, since I've never listened to it (it was never released in my country).