I think DC seems to have a lot of the really good stand alone storys like watchmen and most of the vertigo imprint, but i think i prefer the standard marvel universe to the standard DC universe. I think Image also have a few self contained epics that I really like, such as rising stars, Fell and Wanted.
i think one of the reasons i prefer marvel to dc is looking at the main titles and i may be a bit niave here, I haven't read anything post crisis
DC: batman, superman, JLA, JSA, Outsiders, teen titans
there's no real distinguishment between JLA, JSA etc. they're just different teams with different flashes or different green lanterns. i read a bit of JLA but could never be bothered with the others.
Marvel: Daredevil, Spiderman, Avengers, F4 , X-men, Hulk ,Punisher
So the 3 team lines are all different, avengers is a mish mash of whoever each member has a unique origin, and you've got different dynamics, X-men all have the same origin so writers don't have to think up sketchy origin arcs. And F4 is like a Family, again different dynamics between members. Each team i feel is fairly distinct and has something different to say. Daredevil has got that same detectivey feel as batman (and many the same writers).. And where as superman is invincible, spidey isn't at all and he often gets beaten the crap out of....and everyone loves an underdog.....I'm probably being too unjust to superman here, i like his character in JLA and superman/batman I just don't think i'd ever be bothered to read his solo comic.
but punisher and hulk i find more interesting characters than wonder woman/superboy/ everyone in DC who has the same power
Tho nothing beats super pets