There are so many things wrong with this post that it can be its own thread. Let's start with the basics...
George Perez literally broke the rules of standard comic book storytelling when he and Marv Wolfman revitalized DC Comics in the early Eighties. And, no, not just with The New Teen Titans. A serious reality check is needed here. George frankly transformed himself as an artist while at DC in general and on the Titans in particular. And he did it in a way that none of the other artists you listed have done.
Here's just one:
This image which Perez drew in early 1981 features a series of headshots of the Titans inserted by DC which Perez actually drew in late 1979 or early 1980. The headshots were drawn by Perez to help him get a handle on what the characters were going to look like and also to be used in DC promos. Perez noted (before anyone else did) the biggest problem with them: there's only really 2 images here--a "boy" face and a "girl" face.
You could change the skin color or the hair color, but ALL the faces are the same. Okay, the one exception is probably Cyborg and yes, Starfire has much bigger hair. But you could literally remove Starfire's hair, slap on Raven's hood and recolor the image and she could pass for Raven. Same thing with Robin, Kid Flash and Changeling. Their bone structure--noses, eyes, foreheads, chins and cheekbones--are virtually identical. You could put Kid Flash or Changeling recolored in Robin's mask and they would be virtually identical. And you know what? Comic book artists have been doing this for a century...and they're still doing it now.
But Perez was an artist first and foremost who because of the New Teen Titans' success and his increasing role as a storytelling partner with Marv Wolfman wanted to push himself to do better than that. It started with NTT #8 where he decided to try and actually draw each Titan as distinctly unique human beings. First, with Raven as he sunk her cheeks and raised her cheekbones as well as pushing her hairline farther back, but he tried to make all the characters in NTT look like individuals, like real people.
By 1983, the Titans went from being stock comic book stereotypes of boy face/girl face to being actual individuals. Here is the most famous example which long-time fans all remember vividly:
Fans who read both Uncanny X-Men and Teen Titans (as almost every single one of us did--they were regularly fighting it out every single month at #1 so you weren't "in" if you didn't read both) remember this page from NTT #39 and we remember it well. Not just because Dick Grayson gave up being Robin, either. Artistically, it sent a shockwave through comic book fans and pros. Perez proved his point and did it with actions, not words. Artists were indeed guilty of ridiculously using shortcuts like the infamous boy face/girl face trick.
Look at the difference. It's undeniable. Donna Troy, Raven, Terra and Starfire look nothing alike. Dick Grayson's bone structure is no longer just a quickie, cheap copy of Wally West's. Wally has got high cheekbones and a cleft in his chin. As for Changeling, well, Perez detailed all of this in his numerous interviews with Amazing Heroes magazine: Gar Logan's face was based on a young Mickey Rooney. Each character is a unique individual with different faces, different body shapes and different heights. Bye-bye, boy face/shape and girl face/shape cheating.
Oh, and there's another difference: their bodies are different. George's wife was/still is a dancer so he started drawing Raven's body to be more like dancers he saw in his wife's profession: long arms and legs, very thin, flatter chests. Starfire was drawn as, yes, a straight man's fantasy with a very voluptuous body while Donna Troy physically became what she also was in terms of plot & character: somewhere in the middle between the 2 extremes.
The point and it's a big one: Perez is the first artist to do this on such a large stage in a commercially successful juggernaut of a comic book. Comic book artists used the standard cheats ALL the time and still do. Using one of your examples, I love Ivan Reis. He does beautiful work. But there is no way you can tell me that Mera and Ya'Wara aren't pretty much his standard girl faces. You recolor Ya'Wara and put her in Mera's green swimsuit & gold crown and she could easily pass for Mera. Alright, you'd have to redraw her hair--but that only reinforces Perez's point: the faces stay the same while only the coloration, hair and clothing changes.
A true artist would push themselves to make each character unique in terms of body type (mesomorph, endomorph, ectomorph), height, bone structure and how their bodies move. Stuart Immonen, Mike Deodato, and especially Jim Lee and most of the others you mentioned never go into this type of detail. Which brings us to the unfortunate catch: what Perez did and still tries to do is extremely difficult, takes a huge amount of work and thus is very time-consuming. Those of us who pi$$ed and moaned about 1984's New Teen Titans #2 being 2 months late had very mixed emotions when Perez explained that what took so long was trying to do the opening and ending sequences ALL in pencil with *no* inks--meaning tons of extra work to make the pencils dark enough and detailed enough to be photographically reproduced in the comic. Yes, the result was beautiful, but it required serious delays.
I love Olivier Coipel and Jim Cheung as much as you do, but let's be blunt: no way can you say they ever have spent as much time crafting individualized faces and bodies to the degree that George Perez aspired to do. George is older now; he's had surgery on his eyes due to his vision problems. We are incredibly fortunate that he's still able to draw as well as he does. He's slower now and with his failing vision, we will very rarely, if ever, see the level of detail he used to be able to give us in his prime during the Eighties and Nineties.
But those constantly minimizing and/or mocking the quality of his work fail miserably to appreciate the extremely high level of his craftsmanship and his unquestionably fanatical attention to detail. Out of all those you listed, I would say only Gary Frank or Bryan Hitch even come close to matching Perez's insane devotion to true individualization of characters as well as pushing the forms and structure of storytelling.
And you know what? That's just scratching the very tip of the iceberg. Perez revolutionized comics in ways most fans sadly fail to understand and appreciate. And he's still trying to do that even today on Worlds' Finest.