Peace has never been an acomplishment of men. In the beginning, we fought our own pack, we evolved to fight those of other packs, and eventually other kindoms and empires. Peace and men, naturally, do not co-exist.
I believe that the only way peace could be achieved world-wide is to somehow get level-minded, peaceful ghandi-like (though perhaps more in touch with his people and world) leaders for every country, who don't desire more power than the next. Which is pretty much impossible. It'd be nice, but impossible.
My favorite fairy tale as a child was that of the queen who gave everything to her people; when someone complained, she actually spoke to them face-to-face and explained her options and situation to work out a compromise. No one was hungry, because the queen did not live lavishly. No one fought, because the queen herself was tolerant. No one was poor nor wealthy because the queen distributed everything evenly.
Alas, a fairytale. I'm not so naive to believe that it would be possible, let alone last. The country bordering the queen's came in and conqured all the land