I really can't take very much of Dream Theater. They're good but Images And Words is the only album I really like, Scenes is pretty good but it doesn't do much for me, the only great songs are The Dance Of Eternity and Home.
As far as their MUSICIANSHIP goes, however, I really admire them. And most of the time I just listen to them for Petrucci because I'm a guitarist myself, but generally when I listen to music I do it for the MUSIC, and that's why DT never lasts very long in my CD player. They've got loads of talent but I really don't like a lot of the stuff they've done.
Symphony X > Dream Theater, no contest, by the way.