I think Desire is merely a wish or want.

Obsession is just excessive liking of something or someone and can be in most case detrimental to the obsess-or and its subject.

Love is the ambiguously tricky one, as we use love for simple phrases out of original context sometimes. For example, "I love that car". However, that is not the real love you have but merely used interchangeably with the words that express desiring or admiring of the subject. The other form of love, which is the main one, comes in the form of 1 tree with 2 branches (metaphorically); which is a very strong & liking bond to someone or something that is alive with a heartbeat. The tree I mentioned earlier is a familial one, which is the essence of the original word of love. The first branch being immediate family members as that type of strong like is almost imperishable. The second branch is the partner we find in life. Many would think and say "but that love's not familial" however it is, allow me to explain. This is familial because even though you are not related you will eventually in most cases get married and then have children from there. You have become a familial unit with someone who was not your family to begin with. You will love your partner and your children perhaps more than anything else in this world.