It's not because Marvel is fun and DC is dour.

Age of Ultron ? Boring.

Civil War ? Very boring. There is not one action sequence in that entire movie that can is effective as any scene from Terminator, Terminator 2, even True Lies, the Running Man or lesser films. Why ? Because Marvel plays it cards so safe no one gets hurt, and nothing is resolved. Contrast that with the Viper vs the Mountain.

Back to DC... Zack Snyder only cares about cinematography and making stuff look cool. He is all style, no substance. He can make a memorable montage, like the opening sequences for Watchmen and Suckerpunch, but those movies are very flawed. In Suckerpunch, for example, once you see Baby get hit and fly through 3 walls, then just get back up, all tension evaporates because there are no consequences.