In the late 50's and continuing into the 70's television experienced a boom in popularity due to the lowered cost of owning a set. The dominating genre on TV at this time was the western. At one point as many as 26 individual shows were classified as westerns. This saturation eventually killed the market and shows were cancelled left and right. The variations of the genre continue to this day and westerns have been resurrected on the big screen winning an Oscar along the way. The genre is not dead but westerns today are few and far between, especially on the big screen.
SuperHero films like other genres (western, buddy cop, rom com, sci fi, slasher horror) before have been in and out of vogue, especially over the last 25 years or so. It stands to reason that at some point in the not too distant future we will see a time where there won't be 3 or 4 superhero feature films released in a year and also have shows on competing TV networks. We are most likely in the midst of the golden age of superhero films!
Time will have to pass before we can truly assess the quality and impact of the current slate of films. In the future fans may find themselves yearning for a film featuring any hero regardless of how many villains he/she fights, whether or not he/she wears the comics accurate costume or follows the origin/comic story faithfully. In fact the current theme of connected universes is probably going to be the tipping point.
The MCU (Marvel Cinematic Universe) for example: Quality films bringing in exceptional box office for sure. Yet many fans are focused on the characters appearing together and the cameos more than the individual films. Case in point "[Thor: The Dark World](movie:206462)" as a standalone film it was well crafted, yet because no other heroes came to aid Thor it felt to some as isolated and disconnected. In fact the Captain America appearance was one of the most discussed scenes amongst the diehard fans, even though that was merely an illusion by Loki. However Thor the comic has traditionally been a moderate selling book. Many fans love Thor in The Avengers comics but do not pick up his solo book. Thats normal. "Captain America : Winter Soldier" while an excellent film had the bonus of co starring Black Widow to separate it from the previous Marvel films. Now Iron Man, Black Panther and possibly Hawkeye are going to appear in the next film "[Captain America: Civil War](movie:994409)".
Most solo comic series have the main hero battling all types of foes month in and month out without other heroes showing up to aid him/her. Guest appearances do occur often but on average Thor often saves the day alone quite well. So does Captain America, Iron Man and Spiderman. This trend of teaming up heroes in movies could go either very well or very badly. Many fans will complain when they read that an upcoming film features more than one villain ( [The Amazing Spider-Man 2](movie:508593) anyone) yet they want the heroes to pop in and out of each others films regularly. The average moviegoer is the one the studios are worried about. Sorry longtime comic fans, but you are going to see the film regardless. You give them that big opening day but the casual fans come Saturday and Sunday.
Sure they (average non comic book reading moviegoers) like to see the heroes together too... but to them it is a bonus, not mandatory. Once we get to the point where each film has multiple cameos how will the casual fans tell the difference from an "Avengers" film and a "Civil War"? They won't ..and if history tells us anything, its that in a few years the studios risk flooding the market with too many heroes.
That is why the licensing issues between Marvel, Fox and Sony are not really bad things. If the market dwindles and the studios are trying to find new "events" believe me co-productions will be discussed. If Spider Man were already in the MCU along with X Men and Fantastic Four they wouldn't have those aces up their sleeves in the future.
With "[Guardians of the Galaxy](movie:424073)" being able to bring a little known property to the masses it showed that inter connectivity is not necessary. That doesn't stop fans from wanting Adam Warlock, Nova, Mar-Vell, Hulk or Iron Man in the sequel. The standalone film is in danger of being almost impossible to distinguish from the event film. Hopefully "Ragnarok" will focus on Asgard and Thor with no need for Hulk to show up, but I doubt it.
If done well connected universes (and I think Warner Brothers' execution of their slate will be the deciding factor here) and their over lapping stories and continuity will provide rich , fleshed out universes where people will be able to follow their favorite characters and not need to see every film to understand the plots. It seems though that Marvel so far is beginning to weigh the connections heavier than the connecting points.