Duy: It's so weird to say this, because I distinctly remember fans saying Kingdom Come would be revered on the same level as Watchmen and Dark Knight Returns after some time had passed, but I really think Heroes Reborn was more impactful. Aside from I'm sure getting Jim Lee to where he is today, I think it also paved the way for Marvel Knights (a similar business model but with more expendable characters) and get Joe Quesada to where he is today. The titles that Marvel put out during Heroes Reborn (Thunderbolts being the main example) and the subsequent titles they put under the Marvel Knights banner got Marvel to really start trusting in their characters and elevating them (from C-list to B-list, from A-list to B-list) so they wouldn't rely on Spider-Man and the X-Men anymore, something that was pretty evident at the time. It's hard for me to imagine Marvel Comics, and even, to some extent, DC Comics now without Heroes Reborn. I can't really think off the top of my head any overall movements influenced by Kingdom Come.
Matt: I've only read Kingdom Come. As a stand alone, I enjoyed it and the art, but it's definitely of a time and place and style. That said, Kingdom Come has had no lasting impact on how anything goes on in DC. That's not a downside.
Back Issue Ben: I'm not a fan, but Kingdom Come is unquestionably the better story. As far as lasting impact, beyond Magog and KC Superman being used in later stories, not much. It was very much a meta comment on the extreme '90s comics of the time. Heroes Reborn was an attempt and a precursor to making the Avengers family of titles prominent again. It was a precursor to the Ultimate universe, and that perceived need to start over with a fresh and current take. Many of the elements of Heroes Reborn were later used in the Marvel Cinematic Universe as well. Most importantly, it was a precursor to the downfall of Rob Liefeld as a superstar comics writer and artist.
JD Shofner: Kingdom Come helped form my lasting love of comics. I went from hardly reading any DC comics to researching every character on the covers to find who they were referencing or were homages too. It introduced me to the DCU. So, of course, i am very biased. I think its themes can easily extend beyond its time and place. A harsher America post-terrorist attack, an older generation trying cope with a generation of latchkey kids they created. I believe there are many ideas in Kingdom Come being expressed beyond merely "90s comics suck".
Travis Hedge Coke: Most of the effects of Heroes Reborn on characters and story in comics and movies, seem to be parallel evolutions, instead of copying over (Tony and Bruce as friends, more articulated Iron Man armor, giving Sue more authority, the Human Torch and his action figures, Mandarin as a white guy using orientalism to make his terrorism scarier), while Kingdom Come really redirected Wonder Woman for a lot of people, as Warrior Woman. But, in terms of industry and practices, Kingdom Come's biggest achievement is being a mid-90s watershed for hate and feelings of betrayal re the early-90s (yes, kids, Kingdom Come is an entirely 90s comic), while Heroes Reborn's successes and failures were easily an influence on Marvel Knights, Marvel's next bid to revive themselves, that picked the company up big time, resulting in Quesada's time as EiC of the whole shebang and the Marvel U we have today. A willingness to modify character's dress and behavior to fit the era in which the comics were being made, while it could be decried as "Image-izing," was a huge and necessary leap, more parallel to Batman Year One or Vertigo than to Kingdom Come.
LaMar Forte: It could be argued that the concept of Heroes Reborn had a more far-reaching and lasting influence on the way stories are told today, as well as how business is done. But one could also argue that said influence was of a more pernicious variety. Substituting contemporary stylism for properly executed storytelling only works as long as the sheen is evenly applied, but once it starts to chip on the edges you're going to have to redo the whole thing. Kingdom Come being a response to this type of perspective, which I'd say blends art and commerce a little too much for my tastes, could serve as sound proof of the point because a) Kingdom Come didn't have as much pre or post impact, but it probably wasn't designed to as much as it was to challenge a current model while "doing it right" and b) the remnants of it are still there in DC's narrative, but not much so anybody else's. However, if I were to pick one of these to show someone not into comics the potential and uniqueness of the medium, Kingdom Come is definitely more capable of pulling cargo.