Is Anything A Greater Cinematic Achievement Than The MCU?

Sure, but what I mean is that when we look back at the heyday of CBMS (the way we look back at Westerns as one of the best examples of a type of movie that is no longer made with any real frequency) we will see that MCU was an industry juggernaut in the era of this type of movie. No one's going to say "That Hellboy movie was the top of the heap!" They're going to say "During this time the most prolific and successful creator of such movies was Marvel Studios which ushered in the era of the shared universe of movies, which DCEU followed, which Universal tried to emulate with their Dark Universe, and which even affected the already successful Star Wars and Fast and Furious franchises."

Don't get me wrong, I'm more of a DC guy myself, but there's no doubt that Marvel has taken the brass ring so far in terms of movies. We are currently in the golden age of CBMs and MCU is the industry leader right now.