I've got this theory about art forms - I think it applies pretty well to musical theater, video games, theme park attractions, and even movies - maybe more than that. I'm curious to hear what you think about it.
I think any new art form goes (roughly) through a series of phases:
1. Experimental Phase
When an art form is brand new, things are pretty exciting - people are basically just throwing stuff at the wall to see what sticks. At this phase, a smaller percentage of the population has any interest in the art form, so expectations are low, and people can get away with more. Future fans often look back on this phase with tremendous nostalgia, remembering the surprising successes, but this phase is generally characterized by a very high proportion of pure garbage. Production values are low - there's not a lot of money to go around. Attention from traditional media and from cultural elites is frequently VERY low, even sometimes contemptuous. But early successes start to mount. Some companies start to figure out what works and what doesn't. Lessons are learned, and popularity starts to build. Surprising successes start to mount.
2. Golden Age
Now companies take lessons learned from the experimental phase and mature them - they add money, better technology, more well-thought out processes, organizational structures, and the results are brilliant. With more resources, the things that worked from the early years are expanded on and done RIGHT. Companies are still taking risks, but the costs are starting to get higher - pure experimentalism is waning. The industry seems to be maturing, although at this phase the art form has likely not reached maximum cultural penetration. But within its own new community at least, the art form now seems to have achieved a perfect melding of popular success and critical acclaim.
3. Breakthroughs
And then, at a certain point, one or more big companies decide to spend a LOT of money and a LOT of organizational effort and a LOT of novel technology on the biggest and best effort yet. This combination of maximum resources plus the lessons learned from the early, experimental years marks one or more works that are seen as masterpieces - tremendous breakthroughs in form, technology, or scope. These works redefine the art form, and establish that it's capable of far more than traditionally believed. The potential audience for the art form now expands tremendously, believing that this breakthrough is just one more iteration in the infinite improvement and expansion of the art form. However, the costs of creating similar blockbusters have now skyrocketed, and the barrier to entry for the art form is now higher than ever.
4. Commodification Phase
A split results - the established companies with resources can continue to produce blockbusters, while new entrants struggle for attention. The big companies become tremendously risk averse, as budgets soar. They start to prefer productions that seem like reliable, guaranteed successes - safe bets like franchise installments, sequels, technical advances on familiar formulas. Freshness and novelty are punished more highly, even if everyone claims to want them - failures cost more and are punished more heavily by the larger audience. Simultaneously, smaller producers can't compete in terms of resources and marketing, and so have to rely on innovation - occasionally, this innovation stills scores a success and breaks through to the established companies, but this is relatively rare, and these successes may not be easily repeated, and so leave no particular legacy. The rarity of these breaks stems mostly from smaller companies' own need to mitigate risk - without large budgets, they may start to rely on other mechanisms to survive, such as academia, non-profits, independent financing, and government grants. All of these erode the likelihood of innovations succeeding, because they erode the connection between artistic success and financial rewards. If the artist fails, the artist suffers less consequence, and is therefore less motivated to truly connect with the audience.
5. Stultification Phase/Death
Eventually (sometimes VERY eventually), the extreme risk aversion of the established companies starts to do them in. The audience grows bored of the same things over and over again, and lacking freshness, move on to other art forms. This does not, however, necessarily result in any additional success for the lower-budget independents that now face less competition from big names. Habits learned while trying to survive during the previous phase - reliance on non-commercial funding sources, moral resentment at the broader culture they perceived to have rejected them - cause the art form to dwindle yet further, until it's eventually on life support driven entirely by nostalgia, academic interest, and even a sense of cultural mores - people "should" be interested in this art form because of what it's capable of. Unfortunately for the remaining diehards, people tend to respond better to art forms they do like, rather than art forms they should like.
So how would I apply this template to actual American art forms? Does my theory even work very well? Well, let's see...
Video Games
I would put the experimental phase from the beginnings of garage and university hackers, through the Atari, right up until about the era of the Nintendo Entertainment System, with the golden age really getting established during the 16-bit era. The beginnings of 3D games (Playstation era) represent the first breakthroughs - with the biggest coming with the XBox and PS2, greatly expanding the audience for video games (as well as budgets). At this point, commodification sets in, and has been going strong for a long time. There are occasional hints that some former big players are struggling/declining, but I don't see stultification setting in quite yet.
Musical Theater
I would put the experimental phase through the early twentieth century, maturing into the golden age in the 50's and 60's, when musicals were probably at their maximum combined cultural and financial height. The decline in the 70's admittedly doesn't fit my pattern very well, but the huge blockbuster successes of the Lloyd Webber shows (as well as Les Mis and other mega-musicals) in the 80's seems like a clear "breakthrough" period, greatly raising the budgets and the public's expectation for the form, as well as making a tremendous amount of money for a few players. The Disney musicals and blockbuster imitators of the 90's and 2000's represent commodification fairly well - although success rates seem lower here than in games (Disney with the best track record). Where do more recent critical and commercial successes like Hamilton and Book of Mormon fit in? Couldn't say. Will they spawn successful imitators?
Theme Park Attractions
Theme park attractions have always been higher budget, so the "experimental" phase is necessarily less experimental, but you can still the pattern. Amusement park rides, ghost trains, tunnels of love, etc. take us through the early twentieth century into Disneyland, when Disney launches a golden age with the New Orleans Square attractions - Pirates of the Caribbean and the Haunted Mansion. Disney's death puts an artificial brake on progress until the 80's, when Eisner and Wells open up the floodgates and the golden age resumes aright - with fantastic attractions like Tower of Terror and the Indiana Jones Adventure. I would place the true "breakthough" attraction, however, at Universal's Spider Man, which was such a tremendous step forward that it now seems the virtually EVERY new attraction must imitate it. Budgets are now so high that both Disney and Universal rely almost exclusively on franchises now - will we see stultification in the near future, or will billions more dollars spent on franchises save them?
Film
I know a lot less about film so I could be way off on this, but I see the "breakthroughs" as films like Raiders of the Lost Ark and Jurassic Park - films that showed the success of high-budget continuous action and high-budget computer graphics, respectively. Commodification seems to have set in very strongly over the last decade, with franchises seemingly permanently entrenched - but it remains to be seen whether the medium will truly stultify, as opera and straight plays have.