That's exactly the kind of thinking the world needs less of, and the kind that I was trying to warn readers against in the parent comment. Why? Just why would a worse world for someone else make for a better world for you, if that someone is not your mortal enemy? It just makes for a worse world, period.
The point isn't that you're taking pleasure in their misfortune, it's that you're taking pleasure in your own fortune. "I'm so lucky for having X." If you don't do that, then any improvements in your standard of living or situation in general will end up having no impact on your happiness, since you just get used to them and take them for granted and don't even realize that you would have a million reasons to be happy. And then (in the most extreme case) you'll end up feeling miserable because of something completely trivial, because you're ignoring everything that could make you happy and the only things that can have any impact on your state of mind are negative ones.
Another monthly installment of the rationality quotes thread. The usual rules apply: