Substitutes for Love

I was thinking one day.. why do we crave love of the opposite sex (same sex if you are homo-sexual).

We start out by needing love of our parents... a mother and a father.
We also may or may not get the love of a sibling and other family members...
Yet we seek another kind of love... this basic love is not enough to sustain us.

Next stage comes when we go out into the world... we develop a friend-circle.
They give us love too... the pure love of a good friend is something amazing.
Yet we seek more! A different kind of love we keep on seeking...

Then we find a girl (or boy), if we are lucky, to fall in love with.. if we are REALLY lucky they return our love...
Thus we discover what some people call the ultimate emotion of them all... the emotion of love..

Just like a child demands a new toy once he gets bored of the old one...

My question is.. can we achieve happiness with just one of the forms of love available to us.. do we need all all the forms of love in our live to really smile and feel happy?
Most importantly why do all other forms of love fail badly in front of the love between a man and a woman...
(For example: people leave their parents to marry the person of their choice, fight with their best friend to date a girl...)