If anything I'd argue an atheist or agnostic who is a deeply moral and ethical person in his actions is more impressive than a religious person who is equally deeply moral and ethical person in their actions but is doing so because they're expecting a post-death reward or avoiding a post-death punishment.
Impressive to you. But maybe not to God ;-) Which is precisely the point many Christians would make; but not all religious people.
But your last sentence interests me. Why are you assuming so many religious people are motivated by fear of punishment or for rewards? King David (try reading the Psalms) talks as if he were motivated by loyalty to God and love of God; you can find similar sentiments in many New Testament writings...
Full Disclosure: ...I've not forgotten about those 72 Virginians we keep hearing about ? KABOOM! :-( Cheers!
"King David (try reading the Psalms)"
Wasn't he the guy who saw his neighbor's wife bathing on the roof and had her husband sent to the war front so he could nail her?