Gates vision of "a computer in every home" made computers a common item in most household in developed countries. People are using computers in their home and offices, where would we be without them.
In the same way people remember the Wright Brothers for planes, Edison for the light bulb (yes, he wasn't the first to invent it, but that's beside the point). Gates will probably be remembered for the personal computer.
If he succeeds with the malaria vaccine, it be just another feather in his cap