I disagree with that completely. Buddhism (though sometimes not referred to as a religion at all) is about finding enlightenment. Is that for self gratification? No, it's to simply feel peace with the planet.

Now as for other religions, the majority of them realise that doing good feels good. The Bible teaches people to do good without expecting "treasures". That doesn't really seem like someone hoping to be rewarded.

Regardless of your belief, doing good makes you feel good. It's not selfish to want that.