Hmm, I'm not sure if this is the case, but didn't Zeus and other greece gods Sort of died? (Something to do with entering the next level of existance, and Hercules was left to create another legion of gods?)
On the topic at hand. IMO JLA has a fair chance of beating him, but I still think if he played his cards right and doesn't do anything he would need to do, he'd win. 60/40 for the Olympean god vs JLA.