I guess the main reason I read more DC is because its what I grew up with. The first comic I ever read was Superman 75, the issue where Superman dies. For the next couple of years the four Supes books are all I read. Then I discovered Green Lantern, and some other DC books and a couple Marvel titles (Spidey during the clone saga, I wasn't a Spidey fan and actually liked it, what was I thinking?). Currently I read DC because all of my favorite writers are DC exclusive. Judd Winick, Geoff Johns, Jeph Loeb, and Devin Grayson. I love the continuity thats woven through the books and how much I can relate to the characters I enjoy. I don't hate Marvel, in fact I'm starting to read more and more of it, its just I never tried to read the characters like I have DC.
Here is my current pull list:
Superman/Batman
Superman
Batman (Gone after next issue)
Identity Crisis
JSA
Flash
Teen Titans
Nightwing
Robin
Outsiders
Green Lantern
Green Arrow
Marvel:
Ultimate Fantastic Four
Emma Frost
Aspen:
Soulfire
Fathom: Dawn of War
Ekos
I'm looking for more to add if any Marvel fans give me suggestions.