There is not much I can say here that has not already been said about these two heavyweights in the comic industry. Both of these men broke into
comics, in their own way, as teenagers. In the mid-60's, Adams was looking to get out of comics, and we can all be glad he didn't. His work for DC started as the weirdness of the 60's were starting to wane in comics. His realistic, gritty art style helped usher in a new wave of art to match the new wave of stories coming in. His work in 1969 at both Marvel and DC (X-Men and Batman) were arguably his first projects that would lay out a path of success that would see him become one of the top creators ever.
His work on Batman, and later Green Lantern/Green Arrow, catapulted him to comics fame. GL/GA would introduce the world to social relevance in a big way. As a kid, I remember these comics, and remember being blown away by the clean, realistic art style that really stood above other artists.
Adams' greatest contribution, in my opinion, wasn't his art. It was his active crusading in the industry that helped creators like Siegel and Shuster receive both credit and money for their creation. Superman. Adams cared deeply about creator's rights, and not only was he a superior artist, he had superior ethics.
George Perez was born around 13 years after Mr. Adams and really came into prominence in the late 70's. His work at Marvel and DC landed him some very high profile projects...Avengers, New Teen Titans, Wonder Woman, Infinity Gauntlet, and Crisis on Infinite Earths. Like Adams, Perez had such a clean, beautiful art style that was copied by many. My personal favorite story that he illustrated was "A Lonely Place of Dying", which introduced Tim Drake to readers.
Perez worked steadily until 2019, when he would retire due to health reasons.
Both of these creators contributed so much to comics, and paved the way as influences to many talents. Rest in peace, gentlemen.