The primary difference between relationship love Vs (paternal love, sibling love, and friendship love) is our romantic/sexual desire for our mate.
If you remove sex from a relationship you will have a "great friendship". A sexless marriage is (companionship/roommates) with the same last name. There is no such thing as a (monogamous friendship). We don't call it cheating to have more than one friend or any other type of relationship. It's romance, passion, and sexual intimacy that takes a relationship to a new level.
Having said that, not everyone has the same "sex drive" therefore it is (Very Important) to marry someone who is "Naturally Compatible" with you. To do otherwise is asking for marital problems. I would rank the importance of sex/passion at an 8. One man's opinion! :-)