When it comes to cinematic shared universes, the Marvel Cinematic Universe is easily the biggest. Starting in 2008 with the releases of Iron Man and The Incredible Hulk, the MCU popularized the idea of shared universes in Hollywood. This led to a cinematic universe arms race, resulting in The Conjuring Universe, The MonsterVerse, the DCEU (now the DCU), and, of course, the failed Dark Universe. Whereas crossover films like King Kong vs. Godzilla, Freddy vs. Jason, and Alien vs. Predator were initially seen as gimmicks, shared universes are not only accepted but expected by mainstream audiences.

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