I think if you care about whatever is best or whatever is right, then you are happy as a matter of doing that, and not requiring another reward in order to act in that manner. I actually am sure there is a reward for serving God, but it is not the reward of "getting stuff" (even Paradise Earth (TM)). I think the reward is God's Presence:
Good stuff, bebu, but being a poet I feel compelled to illustrate your remarks.
There's rewards - heaven/paradise, the granting of urgent prayers, or as bebu puts it, "getting stuff" -
and there's rewards: the smell of incense lit in Their honor, the hypnotically restful shine of candles or scrying mirror, the pleasure of preparing a little food- or drink-offering, the beauty of a well-retold myth...
the presence: the flicker of Their fondness or amusement in your mind's eye, the toe-curling power as they overshadow you with a message just for you...
So, in conclusion, what was the question? Oh yes.
Um, any god who does not reward you with his love and company as you serve him ... is a false god. For you.
GentlyFeral
whose altar awaits