relationship and friendship

Sometimes these two types of friends becomes conflicting. Many says that in a romantic relationship the ultimate friendship is there. That is your GF or BF becomes the best friend. However, I think that happens because when you fall with someone in love, you will have to distant many other relationships. Even though you have a best friend, you will have to concerntrate more on your affair and when you really fall in Love you won't see anything else. I cannot think of any difference at the moment other than it's nature. Romantic relationships always between opposite genders while other does not have any condition like that.