I've noticed in the past that the discussions of artwork tend to be more nuanced at the Classic comics sub-forum here at CBR. Modern fans in the main DC and Marvel forums seem to favor... wait for it... modern artists. This isn't because modern artists are visibly better, but because modern fans tend to have more limited exposure to older artists. The puzzling part is that even when they are exposed to some great artists from the past, like Perez, they are unable to recognize the quality. I don't know if this is a related phenomenon, but there have been studies that showed that, compared to adults, teenagers have trouble interpreting facial expressions and non-verbal gestures. Maybe young people are more focused on rapidly scanning visual information all around them and are less able to focus on and interpret detailed visual information. Or maybe console games have had a lasting impact.
Perez is an interesting case. His early artwork was less polished but sometimes had some very innovative layouts. Later, George became more interested in showing variation in faces and body types, but a little less interested in unusual page layouts. I generally enjoy all of his work, but no longer consider him one of the best of the best. Nothing against Perez, but I sometimes appreciate a more stylized effort for certain kinds of stories. For example, Perez is a better artist than Mike Mignola, but I would rather see Mignola's art on certain kinds of stories, like horror or maybe science-fiction (due to that Kirby influence on Mignola). I'm glad that Perez was the artist for JLA/Avengers, because he is great at drawing silver age costumes, superhero crowd scenes, and big fights, plus his artwork showed up during one classic JLA run and two classic Avengers runs.