unless you really like collecting individual issues you've probably saved yourself some time and trouble by being out of the loop. most of the good/better stuff has been re-issued in collections.
warren ellis is one of the better writers of recent days although he does occasionally bomb one. better series are his work in
Superheroic - "Planetary", "Stormwatch"
Sci-Fi - "Lazarus Churchyard", "Transmetropolitan", "Ministry of Space"
Cop Murder Mystery - "Dark Blue"
'Strange Kiss' is bad.
Garth Ennis's "Preacher" received all kinds of accolades. it is not, however, a serious criticism of theology as is often claimed. it does have quite a few high points and it's a seminal presentation of his humor and the themes he often explores.
"Hitman" is more about humor, in fact you have to read the two or three issues devoted to the zombie zoo. hysterical.
'dicks' and the issues about the superhero hooker should be passed by.
Peter David isn't 'excellent' but he is consistently good. he had a long run on "The Hulk" you should read. if you like that you should look for more of his stuff (he might still be doing "Supergirl")
Dave Sim's "Cerebus" goes without saying. no, he doesn't have anything else, he's been doing "Cerebus" for the last 30 years. what more do you want?
Alan Moore's work on "The Watchmen", "Swamp Thing" and "MiracleMan" was all back in the '80s so you might have seen it already. much of his current work lacks focus or tries to get way too cute but he still puts out decent stuff once in a while. but then that's why you go to the comic book store .... you test read the stuff on the shelf. note of interest; both of the movies "The League of Extraordinary Gentlemen" and "From Hell" were based on Moore's comic books.
Neil Gaiman - almost everything he touches is worth reading, even the prose stuff. as an added bonus, he wrote the last "MiracleMan" limited series. "The Sandman" goes without saying.
Matt Wagner's first "Mage" and "Grendel" series were very good. the last Mage series was a serious step down and the Grendel limited series (i have no idea how many grendel series there are but it's a butt load) tend to be uneven as he started farming the franchise out to guest writers and artists.
Adam Warren's writing is almost always both great fun and highly intelligent while his art is heavily influenced by manga. pick up his "Gen13" work and get introduced to the wonderful world of ferret-legging.
recommended Manga coming out now in collections
Neon Genesis: Evangelion
Blade of the Immortal