The Times Freakonomics blog puts out a call for comics quotes, and you can still go over and join in the search:
I would welcome suggestions of what are the most famous quotations of all time from comic books or graphic novels. These could be not only one-time quotations, but also recurring catchphrases.
Many examples in the comments section, and to the surprise of NO ONE, the longest, most comprehensive list is supplied by one Torsten Adair. Go, go, Torsten!