I'm amazed paddy spelled Dream Theater correctly.
My theory is that people who heard DT before getting into heavier music will like them, and those who listened to extreme stuff first generally won't.
I heard DT before any extreme metal, and I liked them a lot for some time, but haven't been a huge fan in a while. The quality of the last two albums also plays a part in this. I am in the minority that thinks Six Degrees was actually really good.
Awake, I&W, and Scenes are all very good, if not great albums. Definitely have a fair deal of emotion in them, contrary to what the DT haters say.