I think Jim Lee is one these artists that really doesn't need any presentations. If you already read some of the DC, Marvel or Wildstorm comics from the 80's to nowadays, you probably stumbled with some of his covers and pages. In my point of view, he's the best penciller that ever worked for these major companies, a truly master of his tools, always pushing further on style and concept.
You can see some more artworks form Jim Lee at his Comic Art Community Profile or at his DevianArt.
I'm a big fan of Green Lantern, since my girlfriend introduce me to Green Lanterns Corp Issue #1 I got in touch with the art of Patrick Gleason. Nowadays, Patrick have worked on other titles at DC comics as Batman, Robin, H-E-R-O, Aquaman, Brighest Day and JSA.
Francesco Francavilla is multidisciplinary italian artist with skills requested by many, he's amazing at almost anything he's working on. Nowadays he's working mainly with Marvel's Black Panther and Captain America and Bucky.
You can see more artworks and updates from Francesco at his Official Website or at his Blog.
Dan Adkins is one of the legends of the silver age of comic books, being a penciler and inker for almost every big comic company. He's one of the responsibles for defining the Science Fiction and Fantasy comics artwork, with a really remarkable and clean trace.
Unfortunately, Dan Adkins don't have a Official Website, but you can see more of his work If you search on Tumblr and you can know more about his story at his Wikipedia profile.