Israel phased the Galil be cause we (USA) were giving them M-16s. Why build great rifles when someone wants to give you ok rifles for free?
As far as accuracy and reliability, it uses the Kalashnikov style gas/feed system (as reliable as it gets). In addition, the rifle weighs around ten pounds and fires a lighter bullet than the AK making it more controllable.
Stopping power: The power some guns have to make you stop what you are doing and get your wallet out.