If you are talking about romantic love, being "in love," the kind that usually but not always has a sexual side to it, if it's real and intense there is room for only one it seems to me, just in the nature of our emotional makeup. The love of children and of friends is something else -- lots of that to go around.
Why? I personally think it gets its intensity from reciprocity -- seeing in the other's face the same feelings for you that you have for him/her, though it probably starts with admiring personal qualities -- personality, intellectual, physical, whatever they are, that for whatever mysterious reason are attractive to you.