Is there a better way to prevent malware than a pretty basic review process (iOS/Mac App Store) and data sandboxing?

And to continue the car analogy, lots of car modifications are illegal for safety and public health (smog) reasons. I think computers are headed in the same direction in the next 40-50 years. The children of tomorrow will think it's absolutely bananas that we used to run unsigned code, because malware behaves much like pollution.