I used to read 2000AD as a kid, and still keep my hand in with the odd book now and then. Its a combination of being too lazy and busy to be bothered with the drip drip of the weekly/monthly issues, so the collections and graphic novels suit me fine.
My tastes tend to be fairly anglocentric, never did like much of the Marvel stuff. Always found the a lot of the artwork generic and dull. I do follow artists a bit more than writers (people I know from 2000AD actually) That said I do have a lot of time for a few writers, like Garth Ennis, fucking love his work. But I'm more likely to be attracted if its by an artist I like. It does help if its a writer I like as well, like Ennis, Moore or Grant Morrison.
I dont mind the stuff Darkhorse & Vertigo put out. Have a lot of time for the Batman though, have to agree about Dark Knight Returns as well. I'd add Killing Joke and Arkham Asylum as classics as well.
If you like Watchmen and havent seen it, should give Marshal Law by Pat Mills and Kevin O'Neill a look. Its fucking mental, a gloriously violent funny satire on the Marvel/DC world. One example is raising an eyebrow about why all these muscle bound men in lycra take young boys as "companions"
The other recommendation I'd make is Preacher by Garth Ennis and Steve Dillon. Kinda defies description, you name it its got it, sex, violence, god, religion, perversion, vampires, conspiracies and even Bill Hicks pops up in it. Seems that tv series from HBO is in the works as well. Read more on
http://en.wikipedia.org/wiki/Preacher_%28comic%29Its a touch naughty, but I have taken to getting stuff from bittorrent. Not a patch on the real thing mind, but quite handy if you want to have a look before you buy, or even for stuff you have already got but cant be arsed to get out the box to read. Its even better for getting stuff you cant get hold of anymore, some stuff I just want to read but have never been able to get my hands on it. Preacher & Marshal Law can be found on torrent.