I am a bit amused all the comic geeks are reacting to the team up with shock and horror, as if DC has not been pairing its two most successful characters together for decades, with equally successful results. The only reason they have not done it onscreen already is because neither franchise has ever been active in film at the same time (Superman IV dealt that one a mortal blow.) There are so many dichotomies AND commonalities between the characters it would be almost inevitable even if they were not by far DCs biggest heroes.

Superman is a(n originally Depression era) small town farm boy turned reporter; Batman is a millionaire urban industrialist.

Superman has inherent nigh omnipotent superhuman gifts; Batman is an otherwise ordinary person with extensive disciplined mental and physical training.

Superman is a stranger in a strange land longing to be normal but accepting duties no other can meet; Batman is a popular playboy and eager vigilante.

Superman is a Boy Scout who refuses to kill; Batman is the Dark Knight who simply refuses guns.

On the other hand, both are orphans, honorable, guardians, dedicated to justice (if sometimes defining it differently) and geniuses.

It works on a lot of levels, because their very different backgrounds lead each down very different and sometimes conflicting paths to the same goals.

Pity the whole thing will probably be screwed up by reduction to a set up for a Justice League franchise. Are you as excited as I to see who plays Aquaman?