Warren Ellis once said "People dislike [Quitely's] art because he draws people as they are, not as we want them to be." Just so; Quitely's people, for the most part, are lumpen masses of cells. Even his superheroes fit that description, sometimes with the added benefit of a sense of nobility, more often with a snide sense of arrogance.
My very first exposure to Quitely's art was a spinoff issue of The Kingdom
focusing on Plastic Man's son, The Offspring. Quitely's style perfectly
suited the pliable, rubber-faced characters within, but he also imbued
the father and son with a depth of humanity entirely in keeping with
the somber nature of the story's plot, essentially involving the end of
the world. I didn't think much about the art at the time, though, and had no idea Quitely would soon become one of my favorite superhero comics pencilers.
Quitely's career high was probably The Authority,
where he brought life to Mark Millar's over-the-top reinterpretation of
the series in the wake of Warren Ellis and Bryan Hitch's departure.
Quitely preserved the sense of scale and pacing that Hitch established,
but he added a seedy, decadent feel that once again meshed perfectly
with the scripts he was illustrating. With deceptive ease Quitely
imbued his superheroes with a sense of power and arrogance, the
apotheosis of which remains his cover to The Authority #13:

Quitely has the ability to make the most wild conceits seem real, from the bizarre worlds created in Grant Morrison's Flex Mentallo (sadly uncollected, but must-reading for fans of Morrison and Quitely) to the ingenius variety of freaks, weirdos and oddities Morrison pumped into his New X-Men
storylines.
New X-Men was where the wheels started to come off of Quitely's career. He had left Wildstorm mid-storyline during his Authority run, and when he went to Marvel and reinvented the X-Men with Morrison, the first few issues were as brilliant as any of the other titles the two had worked on together. But Quitely soon disappeared for months at a time, with less-than-stellar fill-in artists taking over, and eventually when he returned, something fundamental about his work had changed.
Quitely began using "digital inking" to finish his work; no more would true artists using the tools of the trade apply genuine ink (and character, and life) to Quitely's penciled artwork. Instead it would be cleaned and sharpened in the digital realm, and his work suffered greatly for it. The remaining handful of New X-Men issues he turned out, as well as We3 and All-Star Superman, would all be "digitally inked." It worked, more or less, for We3, but it definitely took a lot of the wind out of the sails of All-Star Superman, which still managed to be an above-average look at comics' greatest superhero icon. Most ironic of all, the title still managed to be late more often than not. So how does digital inking save time, one wonders?
Still, Quitely remains in demand, and remains a favorite of mine, despite his latter-day flaws. Perhaps it's the extraordinary detail he puts into his best
work (see JLA: Earth 2 with writer Grant Morrison for proof of that); perhaps it's the perfect sense of scale and perspective Quitely
utilizes, arranging his characters within an utterly
convincing three-dimensional space.
Or, perhaps it's just as Warren Ellis said
-- Quitely draws the world and its inhabitants as it really looks, with
minimal exaggeration or distortion -- without sacrificing the sense of
enormity needed to make you believe a man can fly, or cast reality
changing magick sigils, or grow to giant size only to have his legs cut
off out from under himself (is there a metaphor for Quitely himself in there?).
Whatever it is that makes his art so
compelling, he makes every project worth waiting for. And when you're a
Frank Quitely fan, waiting is a part of the package. But the final
product is almost always worth it.