Deeper, darker songs just tend to be better songs........................ JMHO of course. Not that a happy upbeat song can't be great. But there is a tendency for them to feel a bit overcliched (yes I know I'm a Bon Jovi fan but I can't think of a better word for it ) and artificial. Like short term syrupy goodness for my ears rather than food for my soul and heart.

EDIT: That sounded really daggy.