We love what we can't have because of the same.
We also love something more when someone else has that something and we don't, but the same particular thing becomes mundane when we have it in our grasp.
As amazing as it sounds, one could only know the fact's true value when a person realises this astonishing concept and its far reaching consequences on his/her own.
Just think about it for a moment, don't we always keep wanting and longing for the things we never had? Mostly because we never had them. The same phenomenon can explain so many things like why someone reads a borrowed book, magazine, or even a newspaper with much more vigour than when the same thing belongs to him/her, like why we love the things we steal (when and if we steal) more than the thing we have bought, like why the ice-cream or chocolate or pizza tastes even better when you are eating it from someone else, why people on television look way more desirable than when and if contacted in veridical life, why yearning for someone perfect to fall in love with is more exciting than falling in love with a real person.
The only logical explanation for this would be that since we anticipate a lot from something, we take to be perfect and thus languish for it but and when the realisation that nothing is perfect strikes us and when we actually come in terms with the reality, it becomes very hard for our ego to own upto the fact, thereby adding to the list of complaints and woes. Anticipation, perfection and reality therefore are the unholy trinity in the whole scenario and sometimes when the trinity twines or rather crashes into eachother, the love for the particular thing might take a beating for the worst, breaking the brittle rose tinted glass of expectations involved with it. The same idea can explain why we tend be in love forever with something we have never had or someone we have never known in real life. So the very act of not knowing someone for real and not having the thing you yearn for is the reason behind love for the particular object of desire therefore, to be in love forever, love something you can never have, since anything which you can't have can't let you down.
So is love of yearning more powerful than the yearning of love? Yes, when things are materialistic and thence temporary. Subsequently as most human wants are temporary, the approximation can again very well explain the reason behind a lot of human wants and desires which can inturn explain human miseries and cause for pining like people without money, want money and when they get it, they then lose peace over it and search for peace all over again, sometimes even in lieu of money. May be the whole process of wanting, striving, getting, suffering and losing, in that finical order is the ultimate lesson for all humanity. It may be so that once we truly understand the process, we understand that wanting anything we don't have is the reason behind human excruciation.We as humans live mere human lives because most of us continue to want our insatiable wishes even while on the death bed, all the while remembering to forget that we arrive on planet earth without anything and we leave it the same way, so why should we at all want anything that can't be with us eternally, since we ourselves aren't forever?