few years ago I would say world peace... but that is just unrealistic... even when talking unrealistic (people get decandent in times of peace and prosperity somehow, so it would not work, unless we change the human nature).

for me it would be

1) clean water source for all people in the world
2) access to education and healthcare for all people in the world
3) Gaddafi's head on silver platter... I mean peaceful democratic transition for the oppressed countries