Steve Jobs talents were considerable, and his impact enormous. He made computers usable and elegant, rather than forbidding and awkward. He helped create new markets and market categories with the iPad, the iPad, and the iPhone. No one was better at intuiting what consumers wanted before they knew it, and then crafting devices and marketing plans to create and then fill that need.
Without Jobs, though, there would still be personal computers, and they would be used to the same extent they are today. Jobs didn't invent the personal computer; he refined it. The same holds true for the other great products he oversaw. There were MP3 players before the iPod, smartphones before the iPhone, and tablet computers before the iPad. He refined them and brought them to the masses. But even without him, the technologies would exist, even if not in the form they have today.
Gates did similar work at Microsoft. The products he created weren't as elegant, weren't as refined, weren't as hip, and weren't as well-marketed. But even more than Jobs, he brought computing to the masses. Over the years, far more people around the world have used Microsoft products than have used Apple products. That continues today.
Even more important is Gates' impact on philanthropy, an area in which Jobs fell far short. Through the Bill and Melinda Gates Foundation, he has donated more than $25 billion for philanthropic purposes. He has convinced Warren Buffet to give billions as well, and the two of them have launched a campaign to have the wealthy to give away at least half their fortunes to philanthropy. Gates will have saved the lives and bettered the lives of many millions of people around the world.
He'll be remembered not just for the amount he gives, or convinced others to give, but the way in which he gives as well. Rather than mainly building large libraries or institutions and slapping his name on them, he analyzes the most effective way that the money can be used. Essentially, he applied return on investment analysis to philanthropy. So he will have made the money donated more effective as well.
Jobs was well-known for not being a fan of philanthropy. When he returned to Apple in 1997, for example, he closed the company's philanthropic programs, and never revived them when the company became spectacularly successful. Apple didn't even have a matching program for charitable giving under his leadership, something other large companies do.
So while Jobs will likely be remembered as technology's greatest innovator, with good reason, Gates will be remembered as having a far greater impact on people's lives.