If it isn't, we're all in the same boat, so it doesn't matter anyway.
They've lost nothing.
I have to diagree. If you spend your life in devotion to a diety that doesn't exist you've lost everything!
There is no concrete evidence, anywhere, that man lives on after his seventy or eighty year sojourn on this planet. Therefore all you have, all you posess, is TIME!
If you choose to waste your time giving worship and service to whatever gods you choose instead of using your precious time leading a life that benefits your fellowman and leading a happy fulfilling life then you have wasted the only commodity you have, your time.
There are those who say that worship gives them a fulfilling life and to those I say 'more power to ya!' But as for me, I've got better things to do with the few precious years I have alloted to me.