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.
Praised by some, hated by others, Rob Liefeld is one of those comic book artist that you should love or leave. Anyway, what made me brought this artist here is because of his major influence on the 90's comics, Rob style displays totally the techniques that were developed on this period of comics.
Dashed lines, horizontal panels, flat multi color covers, extreme muscle bodies, big high-tech guns. All this is quite familiar for anyone who read a comic during the 90's, what brings me some nostalgia.
Ron Salas is one my latest discovery on comic book art, his remarkable black and white style reminds me the masters Mike Mignolla and Frank Miller. Let's keep an eye on what this great talent will show us further on future, but for now let's check his latest illustrations.
You can check more from this skillfull comic book artist at his Official Website and at his Tumblr.
You probably know the work of Dave Gibbons by his stunning and majestral artworks on the most famous graphic novel, Watchmen. Although this might be his stepping stone, Dave also did awesome comics for DC and Marvel comics.
Unfortunately, Dave doesn't have a website, but you can see more information about him on his Wikipedia Profile and you can follow Dave's latest projects and news on his Twitter.