This thread has made me really realize the importance of philosophy, and it strikes me as unreal most people don't have the time, or couldn't care less about it..
The original OP was mainly about the thought that if there are millions of flies I couldn't care less about, why should we care about billions of humans? What is the difference? Why are humans more significant than flies?
Hey Pad. I've heard Maddox address this question, and he wasn't far off. Imo, the main reason why humans are more important than flies, or any other creature, is our potential. Humans are (well, some are) fully conscious and as such, we have the potential to master nature. Other creatures are simply reacting to nature's whims, and are not capable of attaining our level of culture and technology. To survive into the future, humanity is going to have to leave this solar system as our sun is going to burn out or go nova. Humans are the only hope ANY of Earth's creatures have of living on indefinitely, no other species is going to develop technology advanced enough to make vessels capable of galactic travel, or learn to bend spacetime to get us far enough away from inevitable disaster. Look how far humans have come in regards to controlling nature in such short period of time: mastering flight (as primates), developing vaccines for deadly germs and viruses, antibiotics, tripled our life spans, amazingly efficient agriculture, splitting the atom and controlled nuclear fission to create energy, built vessels to travel off of the planet and back again and to mars, radio telescopes to view the entire cosmos, light-speed communication around the globe, and mapped our own genome, just to name a few. If allowed to continue we will eventually develop technology to; live without aging or disease, control weather patterns, manipulate spacetime, discover (almost) free energy, change vast areas of the cosmos to be more habitable for life, develop light-speed (or faster) travel and colonize the galaxy and beyond, just to name a few. Cows, bats, or flies are not capable of such things and left to their own devices, they'd eventually be wiped out. Now, some may not view any of these things as important, but I am very excited at our species potential for becoming a major creative force throughout the cosmos. And if all that doesn't convince you, remember Jesus. He said we're more important than the other creatures, why would he lie?