I recently attended a marriage conference led by Les and Leslie Parrot. They talked about three aspects that define love: passion, intimacy and commitment. The passion aspect of love is the desire for physical closeness. The intimacy aspect of love is the desire for emotional closeness. The commitment aspect is the shaping of the will to love no matter what.
They shared an exercise they do routinely based on these aspects of love. They start by writing down on a scale of 1-10 where they are at the moment with each aspect of love. So he may give passion a 6, intimacy a 7 and commitment a 10. She may give passion a 4, intimacy a 6 and commitment a 10. Then, the couple can talk about why they are where they are on the scale.
I will be the first to admit that this little assessment has its limitations, but it may be helpful for opening up the communication lines. My wife and I have yet to try this, but its not because we aren't willing. I'll let you know how it goes when we do try it out.