Eros

You have stolen my heart, my sister, my bride;
    you have stolen my heart
with one glance of your eyes,
    with one jewel of your necklace. (Song of Songs 4:)

The Greek word Eros is the root of our English work erotic which helps us understand and differentiate this form of love from Agape (unconditional love) and Phileo (brotherly love).  This is infatuation that love that attracts us one to another and that love that is ultimately celebrated in sex.  Clearly this love, like the others mentioned, is clearly from God as He made Eve specifically for Adam and God caused their desire for one another (Genesis 2).  This is the love that truly results in "the two becoming one flesh," especially when when properly combined with agape and phileo.  Moreover, we see that God intended for spouses to yield authority of their bodies to the other (1 Cor 7).  God clearly designed us to be sexual and gave us a sacramental relationship in which to properly exercise that love. 
To me, no other form of love is more misunderstood or abused than Eros.  Satan, the author of all lies, warps eros above all other creations by God, at least in my opinion.  Don't believe me?  Look into almost every instance where Israel turned away from God and you'll find at the core an idol in the form of sexual immorality of some form or another.  In Romans chapter 1 we find Paul raging against sinful humanity and in the order of downfall, we see sexual immorality at the core.  
For me, in order to properly love my wife, I've got to perfect all forms of love.  Eros may be where the relationship started, but it is a highly conditional love that depends on sexual attraction.  Sexual attraction is fleeting and isn't a strong foundation for a lasting relationship.  So to properly love my wife, I've got to fully comprehend, embrace, and exude agape.  I've got to be in a position to unconditionally love her so that phileo and eros may remain strong.  agape is the foundation and phileo and eros are added dimensions.  To try to build a relationship on agape or eros as the foundation is to buy into a temporary relationship. 
For those of you that are unmarried, your investment in your future relationship begins now, not when you say "I do."  You've got to learn to fully agape God's people.  You do that by falling in love with God first and foremost because since He is love, this is the foundation for a long and lasting relationship.  Once you have a firm foundation in agape, you're equipped to properly phileo and eros.  Unfortunately, the world teaches us differently.  Satan has sold us a lie that any committed relationship is acceptable or even enhanced by the ultimate celebration of eros - sex.  Don't be fooled by the one who would re-order God's creation.  In the beginning, there was God who is agape.  Learn to agape first and foremost.  Failure to get this right is dooming all future relationships to the fleeting conditions of phileo and eros which are ultimately self-centered, what's-in-it-for-me forms of love which will never last.