Logo: 10/10 (very fluid and somewhat origional, lovely
Metro Background: 10/10 (with the faces, it's just great, and helps seperate them
Bat Backgroiund: 8/10 (well done, but clearly biased)
Tagline: 3/10 (very awkward)
Other text: 10/10 (great font)
Hero poses: 8/10 (very adversarial)
A very VERY good poster... I would suggest a "Heroes collide" type basic premise rather than a detailed "they occupy the same city that's why they fight" type thing. I would also suggest "Heroes Collide" over "World's Finest" so that you don't "give away" that these guys are OBVIOUSLY going to team up to take on the real villains...