Shared Cinematic Universes

I've read a few articles about shared universes in film: those upcoming, some planned which failed to pan out, and other suggestions which have yet to be touched upon by any company but definitely should be attempted.

Currently, Valiant Comics is trying to kickstart its own SCU starting with Vin Diesel's Bloodshot. I just watched it and I feel it's a damned good movie. But that's beside the point.

I was actually surprised to learn that studios attempted an Arthurian shared universe and a Robin Hood shared universe. Others out the gate that fell flat were Universal's Dark Universe (which I still wish they would try, I loved Monster Squad, but it could be made with less camp), X-Men Origins, Amazing Spider-Man tried to go in its own direction but lost audience interest.

I read hints some companies are entertaining ideas like Nintendoverse, Transformers wants to try, Star Wars is taking a break (but they'll try again eventually), etc.

Some ideas that have yet to do more than scratch the surface of "little white... cameos" are such things as Joss Whedon-verse, Slasherverse, the Tarantinoverse, Stephen King Universe, etc

Some that particularly interest me are the Alien/Predator universe, the Cloverfield universe (I still want to see Clover vs Gojira), and to a great extent, the Slasherverse (particularly in the case of Freddy, Jason, Chucky, and Ash Williams). Also Dungeons & Dragons, Magic the Gathering, all that stuff, lol.