What's with all the Clooney hate? I don't get it. He may not look exactly like SJ, but he's an extremely skilled actor with significant range. Having said that, he would struggle to play young SJ.
I like Wiley, but have doubts that he can carry a feature film.
Bale would be a great choice, as he seems to bring it with whatever he does.
I definitely don't want Norton, as he's a guy that I always see as Ed Norton and not the character he's playing. But, according to rumor, he could pull off the prickly parts of SJ's personality quite well, so he's got that going for him.
Robert Downey Jr. could do a great job.
In the end, looking exactly like SJ should not be the overwhelming factor. The ability to bring the energy and verve necessary for the role should be. Given that criteria, I would advocate for Bale or Downey Jr. An interesting, if strange, choice might be Jason Schwartzman. Don't know if he could bring the gravitas, though. Joseph Gordon Levitt (prob only for young SJ, though) could be another choice. Another Nolan-ite, Tom Hardy, could also be a choice.
I've found that, often times, casting choices can seem awful or strange at the time they're made (anyone else remember the outrage at Heath Ledger being cast as the Joker?), but the end result ends up almost wholly depending on the film as a whole, including the director, screenwriter, and co-stars involved. I'm much more concerned about who directs and writes the picture than I am about who plays SJ.