As a rule of thumb, if you look at the combined sales of the three solo Spidey ongoings before the "merge", that of ASM, SSM, and FNSM, and then divided it evenly by a ratio of 3 times a month, it comes to about 65k each. Of course, that is barring the reality of delays for some of that period, as this is taking in 2007's numbers. ASM had been riding on crossovers for years, but the sister books struggled to stay in the Top 40. Now, that means that ASM's thrice-monthly sales can drop all they want, but so long as they don't fall below 65k for each issue, Marvel is at least selling as many Spidey comics as they were in 2007. So far, the numbers post-merge are better than 65k, even if the law of diminishing returns is in play and naturally some creators have more buzz than others on ASM. In pure sales terms, the merged ASM has been a success, even if every issue can't sell within the Top 15.
As for the FANTASTIC FOUR, frankly I am unsure of how to boost the franchise, since the belief of "insert hot creative team, repeat" doesn't always work. I do agree that the lackluster films (and short-lived cartoon on CN) surely didn't help. Of course, IRON MAN's comic hasn't seen a boost from movie hype and it remains to be seen if Fraction's new IM book launches well and stays there. Movies don't seem to be amping up core book sales long if at all. Maybe they once did, back when Marvel films were rarer in 2000-2003 or so, but now with 1-2 every year, they likely don't pack the same oomph. Plus, well, they're hardly new-reader friendly. Marvel is moreso than DC, but only slightly.
As I said in my last post, it could be that Millar & Hitch's pedigree has faded considerably since ULTIMATES 2's long delays. Granted, Millar also wrote CIVIL WAR and that had record sales (even if the line helped keep buzz going). I suspected it was perhaps a combo of this added to the malaise the franchise has had.
Millar, in interviews, seems to sense this notion because he believes the FF family has been stagnant for a while and that has removed the polish from it. This has more to do with roster changes; read the Handbooks for the 60's, 70's, 80's, and 90's and get a refresher course in how the FF altered their team roster for significant periods every decade, even before they were 10 years old as a franchise. Personally I believe it is because the franchise, like Superman, had the misfortune of being innovative for it's time and then watching that innovation be taken and improved upon or done in different ways by countless books, while it remained largely the same to seem "timeless". People laugh about how Franklin has avoided even reaching puberty despite being in continuity for about 40 years (seriously), but this is an example of how long the FF has been kept from growing.
Mr. Fantastic is the impossibly smart uber genius who sometimes neglects his wife. Sue is the ever patient and stoic mother figure, both sweet and fierce when she has to. Thing is the slugging, down to earth pug. Johnny is the overconfident, loud-mouth, wise-cracking ladies man. Every major twist in the formula to these four has not lasted and they always return to status quo. In some ways, you could argue they face some of the same issues that Spider-Man seems to, trying to escape the memory of the 60's.
Writers TRIED to have Johnny grow up, get married, and mature, but that ended in the late 90's and hasn't been picked up after Waid's run (Johnny often is written like it would be IMPOSSIBLE for him to be faithful to any decent woman, much less have been married for years in real time). Every time Thing gets serious with Alicia, something happens (and not for nothin', the way Sharon Ventura has been thrown out of the family could almost be seen as hypocritical, or short sighted). Sue has shifted from bickering Femizon to cliche housewife/soccer mom more times than I can count. And the only major change to Reed is that he has become less sexist as the times have modernized (he rarely says things like "cease your womanly prattle!" like he did in the 60's when Lee & Kirby ran the show). Every major addition to the family vanishes with the next writer or is off into limbo.
Speaking in unscientific, fanboy terms, out of any team for Spider-Man to have joined on a permanent basis to completely negate his connection to the "everyman" and seem to move "up a league" in 2004, it should have been the Fantastic Four. The web-slinger has been connected to the Four since ASM #1, and was the second Marvel hero to battle Dr. Doom. Nearly every time he had a MAJOR superhero crisis, whether it was a living costume, Carnage, or the Sinister Six, Peter would always try to call the Four for assistance. He and Johnny were friends/rivals, written to perfection in Dan Slott's modern masterpiece, SPIDER-MAN/HUMAN TORCH. Their families were cosy. They'd teamed up a bunch of times, Spidey was even on an unofficial "new" incarnation, and the very first WHAT IF issue was, of course, "WHAT IF SPIDER-MAN JOINED THE FANTASTIC FOUR?" It sounds like an easy out, but unlike what DID happen; Spidey joining the Avengers and becoming Tony Stark's gimp, which had all fans reacting with a near unanimous, "WTF!?", having Peter join the Four to make it a Five would be seen as more organic, natural, and defensible by past stories. Plus, Reed was on the same side as Stark in CW and could have easily made an Iron Spidey costume (and could have been seen as an "out of touch futurist" as Stark was).
But, this ship has sailed.
Frankly, having Franklin removed from the stage as a cliche child annoyance is no longer cool and ROBS the series of some potential tension and source of drama. How do Reed & Sue react to their kid hitting puberty and wanting to be a hero alongside them, too? Or even to maybe dating some other teenage heroine? As for Johnny, he needs to grow the **** up. You can be a confident wisecracker without being depicted as an immature dumb-ass. As for Thing, either have him finally get hitched to poor Alicia, or bring Sharon Ventura back into the mix. This family needs to grow and change, and they probably need a big event-esque push, call it a WORLD WAR FANTASTIC FOUR, to help them. And finally, while the Four have always been heroes, the shelves are stacked with superhero teams and maybe it is time they did some old fashioned exploring again, or protecting their realm from nasty threats. Out of any franchise to try to connect to the ANNIHILATION franchise, it should be the Four. I mean, Earth was spared being ravaged by the Annihilation Wave and Great Ultron by ad-hoc space squads and the one time Nova tried to contact the Four about it, they didn't seem to respond. There's story potential here, and it could be built upon.
Of course, SECRET INVASION may be the closest thing we have to that, but it is being seen as an Avengers thing. And maybe that is a factor; Marvel chose the Avengers to boost in 2004, and while that has been a great thing line wide (I guess), it has helped the Four become more marginalized and left in the dust).
About the only other suggestion is to do what THOR did; leave the stage after a truly epic run for a few years, and then return with buzz, an eagerly anticipated A-LIST creative team and a bold new direction (or at least a direction that is innovative in the execution that it can be mistaken as new).