I'm of the same opinion. Not only are we never satisfied, we're also very quick to criticize our society and species. We rarely reflect on our triumphs, but repeatedly highlight our failures. Some monotheists take it a step further, drawing a comparison not only between humans, but between humans and the concept of a perfect being.
I suspect there's a degree of evolutionary pressure in this. An individual who is never satisfied is more likely to be successful than one who is easily satisfied. Without our ability to dwell on the negatives and forget the positives, we wouldn't have invented half the things we have.
To me, our triumphs will likely never out weigh our failures. There are a small group of people in this world doing amazing things. However what is the point if we can't survive as a species? As technology improves, one day making something to destroy the world(bomb, nano-machine, virus, etc...) will be as easy and accessible as buying a toaster and if we haven't evolved mentally by then, none of our technology will mean anything. The world right now could be a vastly better place if people only cared a tiny bit more, but we have been so bought off by convenience that I don't think we ever will.
I'm inclined to be optimistic. Nature has been experimenting with viruses and self-replicating machines for a while now, and has yet to come up with a design that cannot be countered. Bombs are capable of causing mass destruction, but we're still a long way off from having a doomsday device as cheap as a toaster.
I also suspect that, given a century or two, we'll have discovered ways of spreading the risk of catastrophic events. Perhaps by regularly downloading our consciousness and distributing backups across the solar system, perhaps even a few sent to neighbouring stars: "Alpha Centuri Backups - Just In Case Some Jackass Blows Up The Sun".
I suspect there's a degree of evolutionary pressure in this. An individual who is never satisfied is more likely to be successful than one who is easily satisfied. Without our ability to dwell on the negatives and forget the positives, we wouldn't have invented half the things we have.