(or "Can't Stop The Changes")
So, now that we've discussed Batman, Spider-Man, the X-Men, Superman, the Hulk, the Fantastic Four, Man-Thing, the Flash, the Martian Manhunter, the Legion of Super-Heroes, Captain Marvel (both of them), Thor, Captain America, and Daredevil, let's see what's on TV, shall we?
Of course, 'Buffy the Vampire Slayer' isn't on TV anymore, except in reruns. It started out as a movie, then became a TV series (with ancillary books and comics), and now continues on exclusively as a comic book. Why? Why not keep going with the TV show indefinitely? The answer to that question provides a valuable insight into why it is that even the best of TV series don't last as long as a comic or book series. It's all down to the storytelling engine...and those pesky, fickle beasts known as actors.
'Buffy', of course, has one of the all-time great high concept storytelling engines. Sunnydale High is sitting, quite literally, on the mouth of Hell, and all sorts of demons, vampires, and long-leggedy beasties crawl out every week to menace the student body...opposed only by Buffy Summers, who wants to be popular and academically successful, but who has this side job that keeps getting in the way, and her loyal band of friends. Xander and Willow fill the roles of kid sidekicks, providing valuable sources of exposition and convenient sources of peril for Buffy to rescue, and Giles works well both as her mentor, and as a further source of exposition. The series also rounds out with Angel as a love interest/secondary hero, Cordelia as comic relief, and a wide range of good tertiary supporting characters. Heck, it's even got a good rogue's gallery. The Mayor, for example, is an absolutely brilliant villain.
"High school is hell." It's an idea that sells itself. Nobody was ever so popular that the traumas of high school don't have a little hold on their soul, and everyone has some sort of horror story about their teenage years. And all they need to do is ramp that horror story up with a little supernatural horror, and voila! Instant Buffy story, just add vampires.
And if this was where they stayed, it would be a perfect storytelling engine. Indeed, the Buffy comics released by Dark Horse tended to do exactly that. With the exception of a few stories written to fill obvious continuity gaps (how did Giles become Buffy's Watcher, how did the move to Sunnydale go, et cetera), most of the Dark Horse comic series tended to be set during Season Three, the period where the storytelling engine was most stable. Even the proposed animated series was going to be set during the group's high school era. So why didn't they just keep them in high school?
Because actors, unlike pen-and-ink drawings, have an annoying tendency to age. Sarah Michelle Gellar was already playing a character four years younger than her; trying to stretch her high school years out over seven seasons simply wasn't an option. So, three years into the series, Buffy and the gang graduate...and things are never quite the same after that. Which isn't unusual for a series set around a high school environment; high school works because it's universal, but we all go on to do different things after graduation. 'Dawson's Creek' never recovered from having its characters graduate, nor did 'Beverly Hills 90210'...could Buffy break that curse?
It started, in Season Four, by setting up the new storytelling engine for the series. Most of the cast went to the local college...with the exception of Cordelia and Angel, who got their own spin-off series and left big "Cordy and Angel" shaped holes in the storytelling engine. Cordy's role was filled by snarky ex-demon Anya, while Angel's part was filled by an amiable lug by the name of Riley Finn, who also happened to be a part of the secret military conspiracy on campus. The series quickly reshaped itself as a college drama with monsters, instead of a high school drama with monsters...
And then, in Season Five, abruptly dropped the concept. Over the next two seasons, they set up a new storytelling engine revolving around Buffy as caretaker of her family as her mother sickened and died and the writers introduced a new little sister (Magic. Don't ask.) Riley was ditched in favor of promoting Spike, a series villain-turned-reluctant-hero, as a new love interest (and gradually sanding off Spike's edges until he fit into that Angel-shaped hole), the supporting cast changed (Oz, Giles, and Oz-replacement Tara all left during this period), and suddenly the show was a bleak, depressing coming-of-age drama with monsters. The writers seemed to have difficulty coping with the changes to cast, the need to devote time and energy to the 'Angel' spin-off, and fundamentally, with the lack of the high school setting that was the key to the whole series concept.
So in Season Seven, it was back to the high school! Which you'd think would be tricky, since everyone graduated four years ago and the whole thing was blown up, but Buffy returns this time not as a rebellious kid, but as a guidance counselor for wayward teens. This new concept inverts the original paradigm; instead of being about how nobody understands teenagers, it's a show about how adults understand teenagers all too well, having been teenagers themselves. But by this time, Gellar wasn't interested in doing a Season Eight, and so the series finale blew up not just the rebuilt high school but the entire town, while turning hundreds of women into new Slayers.
Which is where the comic picks up. The original concept, "high school is hell", has been left completely behind for Buffy Summers as the leader of a strike team of superhuman women, dedicated to traveling the globe and wiping out supernatural evil wherever it may hide. It's a good storytelling engine, but it does lack some of the universal charm of the original series...but by this point, there's really no going back. That's the thing about changing a storytelling engine. It can be awfully hard to change back if you make a mistake. The only thing you can really do is keep moving forward, and hope you eventually find a new destination as attractive as the place you left behind.