In a recent post on RIP JAGGER'S DOJO Rip devoted a few posts to Marvel's Inhumans features and noted, "The Inhumans always proved to be a hard sell for a self-titled ongoing series."
I had made a similar observation in my review of the 1998-99 INHUMANS graphic novel by Paul Jenkins and Jae Lee:
The Inhumans were introduced in the mid-sixties by Stan Lee and Jack Kirby in FANTASTIC FOUR, and the prevailing wisdom is that they were mostly Kirby's designs. However, subsequent attempts to launch the characters in their own series were largely unsuccessful. Though personally I liked the characters, I found that they were too static and lacked a viable group dynamic. The pattern for THE INHUMANS slightly resembled the Lee-Kirby THOR. In both features, the stories alternated between a fabulous otherworld where most of the characters had super-powers, and visits to the mundane world of humanity. Yet, what worked for Thor-- a central character with a retinue of support-figures-- didn't really work for the five main characters of THE INHUMANS. One reason was that four of the continuing heroes-- Medusa, Gorgon, Karnak, and Triton-- were eternally deferential to Black Bolt, who was not only the leader of their group, but their absolute monarch, and the ruler of all the Inhumans who dwelled in the remote city of Attilan. This meant that it was difficult for writers to evoke the standard formulas of Marvel interpersonal drama.
Now, to pull at these threads somewhat, I should not that a "viable group dynamic" is not a guarantee for success. The Silver Age (roughly 1956-1970) gave rise to a larger number of adventure-teams than had been typical for the Golden Age. One of the few teams that had endured from the early 1940s until the mid-fifties was Quality Comics' BLACKHAWK, and this was the only feature that DC Comics continued, starting in 1956, after allegedly purchasing all of the properties owned by Quality once that company dissolved. It may be no coincidence that Jack Kirhy and Dave Wood initiated another team of uniformed crusaders the very next year, resulting in the CHALLENGERS OF THE UNKNOWN, which endured throughout the remainder of the Silver Age. Then within the next three-four years DC and Marvel respectively debuted JUSTICE LEAGUE OF AMERICA and FANTASTIC FOUR, which both enjoyed more long-lasting success than any team that debuted in the Golden Age. JUSTICE LEAGUE survived even though it did not originally boast any sort of "group dynamic," while the FF practically defined said dynamic. Both BLACKHAWK and CHALLENGERS, which were "old school" in terms of interpersonal drama, were gone by the early seventies. At least one of Marvel's team-books with the new emphasis on drama, THE AVENGERS, prospered. However, a good group dynamic didn't save X-MEN, which concluded its first run in 1970, even though it was resurrected to spectacular success in 1975. And of course a number of solo Silver Age characters from both Marvel and DC also pooped out by the early seventies, notably THE SILVER SURFER, which had received just as much promotion in the pages of FANTASTIC FOUR as had THE INHUMANS.
All that said, the thing that currently interests me most about the Inhumans is that Jack Kirby designed them at a point where Marvel was doing very well with most of its line, even if Kirby himself felt that he was getting the short end of the stick in a business sense. Some fan-sources assert that Marvel had some notion of launching THE INHUMANS as a full series sometime in the mid-sixties, but that this plan was dropped, so that the characters didn't get their own berth until debuting as a "co-feature" in 1970's AMAZING ADVENTURES. I tend to believe that Kirby thought the characters up without much input from Lee when the group appeared in 1965 (not counting the solo appearance of the character Medusa, who had appeared sans origin a year or so earlier). But the fact that Kirby didn't seem to have imagine any raison d'etre for these characters suggests to me that in his own work he didn't focus on interpersonal drama to the degree that Stan did. Kirby certainly knew how to evoke drama and pathos, and he probably contributed his fair share of such moments in FANTASTIC FOUR. Nevertheless, I think he did it largely because that's what his editor Lee wanted, not because the continuing "heroes with problems" was his creative preference. Indeed, most if not all of the "team-books" that Kirby did after ending his collaboration with Lee hearkened back to the "old school approach" of the Golden Age. Whether Kirby did the Boy Commandos or the Forever People, a Newsboy Legion for the forties or for the seventies, the team-members were mostly "a swell bunch of guys," which phrase was once applied to the Justice Society of the forties.
To be sure, Kirby's Inhumans, whether in the pages of the FF or in their own feature (a few of which Kirby wrote and drew), were more dour than brimming with bonhomie. But I'm not sure that anyone who followed Kirby's act with these characters ever managed to give them more complex or evocative characterizations-- even though, as noted above, Jenkins and Lee did a better than average job.