Cancer is a disease that is non-infectious. It comes from within your own body, and when it comes right down to it, you are either highly at risk of cancer or not largely because of genetics and luck (i.e. exercise person who has cancer but a smoker of 60 years is completely fine).

AIDS, on the other hand, is a disease that can be prevented by protecting yourself. While communicable and tragic, the disease has resulted because of miseducation and carelessness (as others have mentioned with sharing of drug needles). The vast majority of Americans with AIDS are the result of those who either a.) shared drug needles and/or b.) participated in unsafe sex with an infected partner(s). Genetics or luck have nothing to do with it.

So I selected cancer to be cured, because I have seen too many people close to me die because of this wasting, evil disease.

Obviously, because a religion fundamentally disagrees with a particular procedure or action, it is the Pope's fault that people don't use protection? Last time I checked, the Pope was simply an advisor, and didn't have control over peoples free will, which I why I think blaming the Pope/Catholicism for the spread of AIDS is a particularly ignorant stance.