They will not be rooting for either of the two main protagonists of the movie because they already know that in the end the two will kiss and make up and form the Justice League. What fans want to see is how epic, destructive, and great the battle between Superman and Batman would be.
Everything else in the film is just a side dish, even if Lex Luthor had something to do with fueling the fire of the battle between the two superheroes. Though it would be interesting to see how Superman and Batman will eventually deal with the villain once they found out that they have been played for fools.
Aside from Ben Affleck, Henry Cavill, Jesse Eisenberg, Tao Okamoto, and Laurence Fishburne, the movie also stars Gal Gadot as Wonder Woman, Amy Adams as Lois Lane, Diane Lane as Mrs. Kent, Jeremy Irons as Alfred, and Holly Hunter as the American Senator. There are still several actors in the film, but those were the ones who appeared in the latest full-length trailer. It is expected that the movie will release a couple more trailers before its official showing on theaters in March next year.
The movie is directed by Zack Snyder based on the screenplay of David S. Goyer as written by Chris Terrio.