Trailers tend to lie, so I may have to withhold my judgement of stuff like Batman v. Superman. I will say that the trailer seems really crunched in: there are a lot characters and setup for a Justice League movie, when the film should really just focus on, y'know, Batman against Superman. Unlike the MCU, the DC films seem keen on plowing ahead without establishing characters in separate films beforehand. The original Thor, Hulk and Captain America films perhaps don't hold up as well on their own, but they at least let the title characters breathe. Inserting the origin of one character into a film about another character isn't as effective as having two separate origin stories that funnel into a third. Peanut butter and chocolate may taste great together, but the novelty comes from the fact that peanut butter and chocolate were already individual things to begin with.
In general, I love the idea of a shared universe in which individual entries have to adhere to or expand on what already exists. It's a bit mind boggling to think that Pixar has to write a whole new world from scratch for each non-sequel movie, for example. Does each Pixar story have to take half a film to explain how the inanimate or non-sentient entities are now talking characters? Or would it be easier to establish an overarching force that set all the films into motion? I'd like to think the latter would allow more screen time to develop the characters and plot of the individual movies. There's even a wacky theory that all Pixar movies are indeed interconnected. While the supposed connections are humorous, they fail to serve a narrative function the way the MCU does.
My webcomic is currently developing an expanding universe. Each progressing story arc is leading to a huge Avengers-style mashup. This started off mainly as a homage to the concept of shared continuity in general. The more I researched outside webcomics to incorporate into my own, the more amused I was at how well the respective mythologies fit together. The whole idea of a backstory is really just to establish the rules of the world in a way that doesn't interfere with the immediate narrative. I personally would love a slew of webcomics that all pulled from one central toolbox, yet spawned their own stories. The next best thing for me is to just write my own narratives that mash together existing webcomic characters unofficially.
I guess this also ties into my love of mashups and remixes in music. I enjoy re-producing, not simply as a way of celebrating the original artist(s), but rather to present a "what-if" scenario. In an alternate universe where all art is blended together, would Taylor Swift mix seamlessly with Jay-Z? Or what if the Funky Drummer was hired in every studio to record his immortal riff, regardless of genre? Questions like this are why I fire up my workstation.