Batman will perform the best at the box office, and it won't even be close. It's the conclusion of a trilogy, while Avengers and Spiderman are the beginnings of new series.
If I could only see one, I would probably pick Batman because its last of the Nolan films, but If I'm being honest, I'm probably most excited about Avengers. Its just something that has never been done before in cinema.
I absolutely hated the Raimi Spiderman films, but this one has caught my interest.