An Indomitable Will
The green lantern corps are probably one of the most consistently well written comics in DC, probably just under Batman (Because well, he's Batman!). Events like Blackest night are still fresh in my mind as some of the best crossover events ever written (and yes, I love Geoff Johns).
Looking at the green lanterns themselves, you can see why they have so much appeal. A paramilitary organization whose aim is fighting the darkness of evil anywhere in the universe with the light of their will power. It is the modern story, where human will power is considered inherently good, and evil is something "out there" to destroy if we only keep trying.
It's telling that this is the particular part of the (badly named) emotional spectrum that the guardians of the universe settle on (they are self appointed, with no higher authority than themselves, which tells you a lot). Will is the "least emotional" part of this spectrum and considered more stable (It's probably a good idea to wonder why it's considered an emotion anyway, but that's digressing). It is also morally neutral. All this goes well with the Guardians forsaking of emotions for their "logic".
All this is inherently nihilistic, and definitely cannot sustain itself, which is why the damage the black lanterns inflicted on them during the blackest night event was so devastating. The end of a will turned on itself is an abyss, it's death that awaits it, and only life (even in it's warped interpretation in DC) that can defeat it, life that not only includes will power, but infact actual emotion, and love.