If given full liberties in expenses with the premise that one disease will be cured, which disease would you choose?
It's one of those questions that doesn't work without context because it would depend on how broadly diseases were defined. Is cancer a single disease or a single type? If the latter, would that be by location (breast, lung etc) or histology (adenocarconoma, squamous cell carcinoma)? Is addiction a single disease, or just alcohol or heroin addiction?
So I like skado's answer - "aging" covers the majority of serious diseases as many are wholly or largely occurring in older people (especialy cancers).
I would cure by prevention most diseases by replacing polluters technology with green jobs
Cancer and AIDS are obvious choices (especially for cancer- how many subtypes of cancer are there. For selfish reasons, i'd add Type 1 Diabetes.
@SaintChris I concur.