Let's settle this once and for all: DC vs. Marvel Tournament

Off the top of my head...that Zack Snyder doubles down on a dark, oppressive tone that, as Neverending said, attempts to "deconstruct" its two main heroes (we can argue all day over whether or not we thought it was successful, but my point is, it makes the effort).  That it blithely does away with Batman's no-killing rule.  I know lots of fans hated that, but I personally didn't mind it, because I thought it fit where the character was emotionally at that point in his life.  Plus, it helped give us that rad warehouse fight scene, which is one of those kinds of fight scenes that made me want to stand up and cheer when it was over.  And even though we knew it was obviously going to be reversed/undone, the movie ends on the downer note of Superman being dead.  Those kinds of big swings.  BvS OBVIOUSLY has flaws, but I can find just as much in there where I can look at and go, "Well, Zack, I can't accuse you of phoning this in."  It also at least attempts to tackle a wider variety of themes.

The Avengers, while a good movie, still feels like another relatively safe MCU movie by comparison.  The biggest swing it takes is probably killing Coulson.  I'll acknowledge at the time that it felt like a more permanent death...until just over a year later, when they resurrected him to lead Agents of S.H.I.E.L.D.  So the movie's biggest shock is now unimportant.  Let me be clear that I do like The Avengers, but it never struck me as anything overly impressive or significant outside of the fact that it was the first comic book movie to bring together multiple heroes from separate movies.