This was my ranking almost a year ago:
1. Six Degrees of Inner Turbulence
2. Scenes From a Memory
3. The Astonishing
4. Images and Words
5. Black Clouds and Silver Linings
6. Train of Thought
7. Awake
8. Dream Theater
9. Systematic Chaos
10. A Dramatic Turn of Events
11. Octavarium
12. Falling Into Infinity
13. When Dream and Day Unite
And this is what i'd rank now (and my favourite song on each album):
1. Scenes From a Memory - Finally Free
2. Images and Words - Surrounded
3. Six Degrees of Inner Turbulence - Blind Faith
4. A Dramatic Turn of Events - Breaking All Illusions
5. The Astonishing - A New Beginning
6. Black Clouds and Silver Linings - The Count of Tuscany
7. Systematic Chaos - In the Presence og Enemies pt. 1
8. Train of Thought - Stream of Consciousness
9. Awake - Voices
10. Dream Theater - Illumination Theory
11. Octavarium - Octavarium
12. Falling Into Infinity - Hollow Years
13. When Dream and Day Unite - Ytse Jam
The most dramatic turn of events was A Dramatic Turn of Events