I have a confession: I'm a Marvel Whore, but a repentant one. I want to spread out to DC or another, smaller company, but I don't know exactly what's good or I'm intimidated by lack of universe history (especially with DC). I've started branching out a little with Y:The last man (loved it and bought all the trades) and have read/enjoyed Watchmen, Batman: the killing joke, and Superman: red sun (or was it son? I misremember).
To help with any advice here's a small list of my current marvel favs:
Thor, JMS actually doing justice to a character
Nova/ Guardians of the Galaxy, Abnett and Lanning are just simply awesome, even with lame SI tie-ins
Avengers: Initiative, Slott and Gage=good
Thunderbolts, villain based stories=great
pretty much anything written by Matt Fraction