Marriage is a sacred vow between A husband and A wife. In short, you marry someone you are ready to share your life with and with that, you should dedicate all your life to her or to him.
Wouldn't it be ironic, to marry more than one wife or more than one husband? In respect to other culture where they practice polygamy, I don;t think that it is in a great advantage for it might ignite jealousy, and envy towards one another. They may say that they have equal treatment and the likes, but it is unavoidable that conflicts will happen between wives or husbands.
If love and devotion will be put into mind, I think, it is the best to marry only one person where you will share your everything with her/him forever.