I think everyone is going to give you a different answer. The Morrison people will say All-Star, etc. etc.
Personally, I'd go with Hush. Beautiful art that featured Jim Lee's return to the medium (he took it serious, too!); and Loeb wrote to his style, digging out all the toys.
The reality is that you can't go wrong with any of the three, but if you're a Batman guy, just hold off on the All Star.