...but also for the fact that he has standardised the way in which we use computers, so that virtually anybody can switch a computer on and do what they need to.
Hell, before DirectX, you needed to be a fairly adept at working jumpers on mainboards and videocards just to get a lot of games to work. Several major manufactures of computers, just as many different OS's custom drivers for those native OS's....no matter how much hardcore opensource users complain about Windoze or whatnot, it's a world standard that revolutionized PC's to a far more open and accessible medium than would have been otherwise.
He may dominate the market but have you tried to use linux? if everyone was trying to use that then we would be stuck 10 years in the past. That and being in the dominant position he can push ideas into the mainstream much easier (witness, plug and play, easy to set up networks (thank god!)
I've always used Unix OS's far more than either Windows or Linux, and I think it's the better of the three. However, I do realize that the Windows platform is a hell of a lot more accessible, though.
It's easy to bash Gates for having so much damn money, but some facts do remain that most people overlook. He's had quite the effect on this world, affecting it to the point that I would even say was major. Microsoft's protocols and standards are what helped shape curren global telecommunications and brought about the connectivity and accessibility we enjoy all around the world today. Hell, William Gates the Third more than deserves the honor of being Knighted.