The short version; 'Superman/Batman: Public Enemies' is an explosively enjoyable and stupendously stupid romp through the Superhero battlefield.
You really don't need to know much more than that. The title clues you in as to whether you're predisposed to liking it (I partially am), its typical of DC animation that its full of well animated destruction, however, it also finds itself lacking in the story and character department. I'm a Batman fan, at least in regards to animation, and one of the compelling aspects of that character is his intelligent approach to problems. This is not that movie. This story is essentially an excuse for a series of knockdown brawls, pushing anything resembling interesting character moments or intricate plotting. However, and its a big caveat, is that those brawls are awesome, and the roster of characters is some impressive fan-service, and it delivers some big and silly blockbuster entertainment.