As for the "too many books", I think the thing with X-Men or Avengers is that you have so many characters who can qualify as a member, you gotta put them in their own book. otherwise you end up like Fraction's X-Men where they put hundreds of mutants on one island, but its 90% Cyclops and Emma Frost with various X-Men sitting in the back as wallpaper.
It goes back to around the second half of Claremont's Uncanny X-Men run. New Mutants was the first alternate X-Men ongoing, but I thought that one had a pretty legit claim. Claremont didn't ever get to do the whole "O5" thing with the teenagers going to school under Charles Xavier and training to be X-Men(I mean, could you imagine Storm and Wolverine sitting in class getting demerits and shit?), and it was a completely new cast of characters that stayed in their own world and you didn't have to buy if you didn't want to. And hey, those issues Sienwickiz were the shit.
I think the beginning of the end was when they launched X-Factor. For some reason, despite the fact the the Original Five X-Men were BORING AS SHIT and nobody cared about them until the Roy Thomas/Neal Adams years before being completely eclipsed by Claremont's tenure, there was some nostalgia for these pack of characters(that continues to this day with All-New X-Men...I can't explain it). They wanted them to have their own book, even though Jean died in that really big story everybody liked and Cyclops was married to his wife and had a kid on the way. But Shooter wants what Shooter gets, so Jean comes back to life(in a completely different book) and Cyclops ditches his wife and child so they can do this 05 book.
Nevermind the whole concept of the original X-Factor is pretty stupid when you think about it for more than five seconds. The characters (chiefly PR man Hodge) suggest they are turning anti-mutant sentiment around on itself, using it to actually help mutants, but none of the former X-Men seem to realize just how much the seemingly-legitimate X-Factor business model will fan the flames of anti-mutant sentiment, reinforcing the public notion that mutants are something to be feared and hunted down. Furthermore, no one addresses what will happen when X-Factor is hired to capture a villainous mutant who needs to be locked up, as opposed to mutants being wrongly persecuted. Finally, while lip service is paid by the characters to the idea that the obviously-mutant Beast and Angel can't attend meetings with clients and that, while operating as costumed heroes, they need to be careful not to be associated with X-Factor, no one seems to recognize the fact that Angel is a known mutant, and that his money is all over X-Factor even while he operates alongside the others as a costumed hero, meaning it won't be too hard for anyone to make the connection.
So the book concept is bad, the actual stories aint much good, and it kinda pisses on Cyclops' characterization and Dark Phoenix Saga's ending, just for a nostalgic cash grab. They had to LITERALLY demonize Maddie and make her into the bad guy so Cyclops and Jean could be together again in Inferno. lol
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For single characters, I think TWO should be the max. Amazing and Spectacular Spider-Man? OK. But do we need an Adjectiveless and Peter Parker, too? Crossing over all the time with various creative teams, meh. In the early 2000s, the satellite titles Peter Parker/Spectacular/Friendly Neighborhood just didn't sell very well compared to Amazing. Personally, I'm a huge fan of how they did it with BND/Big Time/Superior/etc; you got ONE book starring the adventures of Peter Parker, and it comes out 2-3 times a month. That's the only book you gotta follow.
