[kylactus]

Yeah I think Captain America's powers have been retconed to explain that the "serum" was in fact a virus, because a serum, as a drug would wear off and metabolize leaving him powerless. But adding to your point on radiation, spider, and cosmic ray poisoning, most people I've seen that were born "mutated" had well less than "Uncanny" powers, and more commonly severely debilitating handicaps. don't overthink it kids, Its fiction, its fun and it rocks. Plus who amongst us has not had the joy of being bitten by a painfully venomous creature and saying jokingly as the wound burns "maybe I'll get superpowers!"