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.
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.
Eduardo Risso is a worldwide acclaimed argentine comic book artist, most known for his work with Brian Azzarello on the Vertigo title "100 Bullets" , winner of the Eisner and Harvey Award.
He have been working for major comic companies as DC comics, Vertigo and Heavy Metal on the past 20 years, recently he worked on the highly anticipated comic "Before Watchmen". You can see more from Eduardo at his Official Website.