Whoa, no mention of Jack Kirby's Fighting Fetus?

Wolverine had a hardcore, "bad boy" coolness about him, certainly, and that issue where he singlehandedly takes down the Hellfire Club when all the rest of the X-Men had been captured was amazing to read. It was like you could SEE a star being born.
But there have been some original characters since then.
Not all of them are "truly great," but you can't blame the guy for trying. Most of the villains later-period Kirby created in the 1970s fits this mould, like Doughboy in CAPTAIN AMERICA.
Though the execution was uneven, the idea of Booster Gold - a guy becoming a superhero for money and endorsements - was certainly an original one. Then you have Sleepwalker, who lasted for several years and was a cult favorite, who was a creature that sprang into existence only when his secret identity was asleep and dreaming.
The great Roger Stern, Superman's best Iron Age writer by a long shot, gave the Super-Mythos the gift of Maxima.
I'd feel guilty if I didn't mention the Kurt Busiek characters that he created in the 1980s (before he became the big superstar he is today) like the heroes of the LIBERTY PROJECT. The concept itself wasn't wildly original, but you had a character like Slick, who had powers over friction.
That's the hardest thing you can possibly do, in superhero comics, is create a power nobody has seen before, or a power combination nobody's seen before. There was Jolt, who was a super-athlete, but also had an electrical release touch, or Charcoal, who was a big rock guy a la the Thing, but who could flame his body and fly, too - not behavior you usually see in your big strong guy.
Then you have the heroes of Busiek's Power Company, like Striker Z, who was a stuntman whose power is being a "living battery" to power an arsenal of gadgetry, or Skyrocket, that has a suit that changes energy from one type to another. When somebody asked Striker Z what he thought of being a superhero, his response was, "I ah. just never thought about it."
Englehart's STRANGERS had many original characters; with the exception of the robot girl that shoots electricity and the "ham and cheese sandwich" personality Atom Bob, just about every character on that team was an original idea. The guy that burns with rainbow colors, each color giving him a different superpower, for instance, or Elena a fashoin designer and her ability to hit anything.
I'm a big fan of Kurt Busiek, but I'm not as big a fan of his ASTRO CITY as a lot of other people are, because it depresses me to see someone as obviously bubbling with ideas and originality as Busiek waste his time with stories that feel like ideas he pitched to DC or Marvel and were rejected. "Hey, look, there's Superman and Wonder Woman out on a date!" (wink, wink) The best issues of Astro City are the ones that quite clearly explore an idea nobody has done before: Junkman, for instance...and the idea of a super-villain that just GETS AWAY with it, was as magnificent as it is original.
I may be the only person in the universe that prefers POWER COMPANY to ASTRO CITY. So be it.
A while ago, SuperMonkey and I got into a conversation where somebody made the observation that great new ideas aren't very common. SuperMonkey argued this is typical of writers and artists just not caring.
My response was that, since the DC and Marvel universes have been established for some time, pointing out that the flow of new ideas is slowing...is fundamentally misunderstanding how worldbuilding and serial fiction "work," and in fact, after a certain point, new ideas are not even necessarily
desirable.
I used the example of JOURNEY INTO MYSTERY: it's exciting to read the first few issues because they throw out a new idea every issue or so: the Odinsword, the portal to Olympus, Lady Sif, the Warriors Three, the Flying Trolls of Thryheim, etc. But after a certain point, we start to understand what Asgard looks like. After a little while, it would not be possible to introduce an idea like a new cousin of Thor, for example, without severely trying suspension of disbelief. This is why that Kyle Rayner villain introduced by Ron "Gibbon" Marz was such a horrible idea: if Darkseid had another son, don't you think we'd KNOW about him by now?
To use another example: in the original STAR TREK, beings like the Romulans and Klingons were introduced in the first season, because that's really the only time they COULD have been introduced: when we're learning what the Star Trek cosmos looks like. Something as important to what the Trekverse's shape as the Klingon Empire CAN'T just be introduced at a later point in the game. Thus, when "new" enemy races were introduced, like the Ferengi and the Borg, they had to devote some time explaining why we'd never seen them before.
This isn't "laziness" or lack of innovation. Why create a new race when beings as established and as charismatic as the Klingons would do just fine for the story? In fact, the only reason Next Gen had to create new bad guy races was because the Klingons weren't available anymore.
Returning this conversation back to comics...well, let me put it this way: I love the Mad Thinker. Why move heaven and earth creating a new character when an established character with as much history, goodwill, and interest as the Mad Thinker would be perfect for the story you're writing? This is what I mean when I say that after a certain point, innovation isn't necessarily desirable.