a) bringing affordable / usable home computing to the majority (something I usually see Jobs credited with)
b) using a large amount of his vast wealth for good causes (I never heard of Jobs doing anything).
Several parties have said Jobs donated to causes, but would often do so anonymously. Known is that he donated to the Democratic Party and to cancer research.
As for Gates: he is once again the richest person in the world. He could give away half of his wealth and he would still be in the top 6. Let’s not think too long about how he amassed his fortune, but I’ll give one example: under his leadership at Microsoft, he ’gave away’ tens of millions of Windows licenses to schools, so that kids would grow up being used to using Windows. It was presented as charity and Microsoft received tax benefits from doing so.