Coming from someone that is very involved in the Polyamory community, for us, it is not ALL about sex with multiple partners. It is all about having real meaningful relationships with more than one person.
Sparkleboots was right about one thing. No one person can fill all your needs. It is unfair to expect people to live up to our expectations. In the Poly world, we enjoy the qualities that each of our partners offer. Love is not a selfish emotion, which is the case in most monogamous relationships. It was designed to be shared freely to all.