This is a complicated, deep question if you really think about it. I have often thought the same question. What I think is that no matter if you are religious or not, if you are a decent, nice person and you live right then you live the same good life as the believers, and you reap rewards as well (I do believe in Karma).
My parents are religious and I have seen them in too many ups and downs. They do not live a better life than the rest, I observed. They attend church regularly and they are good people (most of the time, given the psychotic tendencies that runs in my family). But no, they don't live a BETTER life, but SOME live a more 'holy' life than others, but NOT better.