I'll answer the question based on my first reaction.
Alas, my ideal world would be a dystopian hellhole. I distrust authority, and I distrust it most when it's granted to me. I don't think this is the best of all possible worlds, but it's a decent start, and I envision only incremental changes. If I could reconstruct a world from scratch, I'd break it.
But the two things I want to see change in this world more than anything else are women's education and the end of energy from fossil fuels. The first is not just a matter of human rights, but the surest proven way to avoid overpopulation, and it's largely because of better women's education that population growth is slowing down. Without keeping our population in check, we're doomed to endless strife. The energy issue is the other tough nut to crack, the other issue (besides population increase) that leads to so much trouble around the world.