Superman gave it to him. 

It used to be Lex Luther's ring.  When it was confiscated from him Superman gave it to Batman because if he were ever to go crazy despot or mind controlled Batman could take him down. 

Batman by far. The last version of each of their movies proves it. Superman Returns was an awful horrible movie, where as Batman Returns was an amazing, badass movie.

"Batman has Kryptonite so he could beat Superman in a fight"

That fight would go something like this

Batman: I'll use this Kryptonite on Superman

Superman: What's that? My super hearing tells me that Batman intends to use Kryptonite on me, time to fly in to space and hurl a giant asteroid at the city of Gotham. Boy, that sounds like hard work... I should bring an apple in case I get hungry.

While it is true that Superman has a huge potential as a character, like Kasz pointed out, the potential has not been much utilized in comics or on film, whereas the different aspects of the caped schizophrenic and his clash with the real world have been portrayed in some of the greatest comic book story lines and comic book film adaptations ever. For example, have a look at the two best Batman movies: Batman Returns and Batman Begins. I love the way they come to display the character from totally different angles: one is portraying Batman's world through his own eyes and the other through the eyes of the society.

In Batman Returns we see Batman as he sees himself and the world around him. This is a fantasy world, a world adjusted and created by Batman himself, showing his incapability of love, and to cope with the responsibilities of everyday life. Instead he dreams of a freak villain and even freakier love he can relate to.

In Batman Begins, we see his actions from the outside. A man's existential search of self and blooming schizophrenia make him collide with the world, and trying to get a hold of what he feels he ends up creating Batman, a dark creature of the night that can do everything he wishes he could do as himself. I would have loved to see the concept to be taken even further, but I think we will get deeper in the next movie as Batman confronts somebody just as lost as he is in the Dark Knight. Nolan has stated that he's studied the Killing Joke as one of the references to the chemistry between Batman and Joker and that makes me quite hopefull for the outcome. If you haven't read Killing Joke, do it now.

I'm not a great fan of American super heroes, but while Superman embodies everything that's wrong with them, Batman is mostly just guilty by association.

I am nor superman neither batman but at least aidman lol.

Well I like batman more Gothem City more beautiful than small ville lol

Superman is a hollowed husk of 50s patriotism. Batman is the Dark Knight.

Hellz yeah.

Batman, just because I like the last movie better that the Superman's